Convert length, weight, volume, area, temperature, speed and pressure from imperial to metric units with UK-friendly 2026 reference tables and practical building, DIY, property and everyday examples.
Imperial to Metric conversion guide UK 2026 — Quick Reference
ThisImperial to Metric conversion guideis built for UK users who regularly meet both measurement systems. UK road distances are still commonly shown in miles, personal height is often discussed in feet and inches, body weight is often given in stones and pounds, property and flooring quotes may include square feet, and older building drawings may use inches or imperial brick dimensions. At the same time, most product labelling, technical design, building specifications, education, science, trade documentation and manufacturing now use metric units.
The aim of this page is not only to work out a number. It explains which imperial unit is being used, what the exact metric equivalent is, when a rounded answer is acceptable, and where confusion can happen. This is especially important forUK construction, DIY, landscaping, property, recipes, fuel economy, gym weights, vehicle speeds, garden areas and material estimating. A tiny rounding difference might be irrelevant when converting a person’s height, but it can matter when ordering worktops, flooring, plasterboard, pipework, steel sections or concrete volumes.
2026 Update — Metric First, Imperial Still Common
For UK retail and trade communication, metric units are normally the main measurement. Imperial units can still appear as supplementary information in many contexts. GOV.UK guidance on units of measurement says imperial units may be used voluntarily for selling packaged or loose goods, but a metric measurement must also be shown and the imperial indication must not be more prominent than the metric one. This makes accurate imperial-to-metric conversion useful for both customers and businesses.
- Measurement: Length; Imperial Unit: 1 inch; Metric Equivalent: 25.4 millimetres; Typical UK Use: Exact Joinery, screens, pipe sizes, older drawings
- Measurement: Length; Imperial Unit: 1 foot; Metric Equivalent: 0.3048 metres; Typical UK Use: Exact Height, room sizes, estate listings
- Measurement: Distance; Imperial Unit: 1 mile; Metric Equivalent: 1.609344 kilometres; Typical UK Use: Exact Road distance and speed
- Measurement: Weight; Imperial Unit: 1 pound; Metric Equivalent: 0.45359237 kilograms; Typical UK Use: Exact Body weight, shipping, gym plates
- Measurement: Weight; Imperial Unit: 1 stone; Metric Equivalent: 6.35029318 kilograms; Typical UK Use: UK Common Body weight
- Measurement: Volume; Imperial Unit: 1 UK gallon; Metric Equivalent: 4.54609 litres; Typical UK Use: UK vs US Fuel, older manuals, liquids
- Measurement: Area; Imperial Unit: 1 square foot; Metric Equivalent: 0.09290304 square metres; Typical UK Use: Property Flooring, rooms, panels
- Measurement: Land Area; Imperial Unit: 1 acre; Metric Equivalent: 4046.8564224 square metres; Typical UK Use: Land Plots, farms, gardens
Length and Distance Conversion — Inches, Feet, Yards and Miles to Metric
Length conversion is the most common reason people use an imperial to metric guide. In the UK, everyday language still uses phrases like “six feet tall”, “a twelve-inch shelf”, “a three-yard skip”, or “five miles away”. However, technical drawings, product specifications, building regulations, appliance sizes, kitchen plans and engineering tolerances are normally metric. That means converting correctly between inches, feet, yards, miles, millimetres, centimetres, metres and kilometres is essential.
The most important exact relationship is1 inch = 25.4 millimetres. From that, 1 foot equals 12 inches or 304.8 millimetres, 1 yard equals 3 feet or 0.9144 metres, and 1 mile equals 1760 yards or 1.609344 kilometres. Because these relationships are exact, the conversion guide can safely be used for repeatable working. What changes is the level of rounding you choose for the final answer.
DIY & Joinery
Use millimetres for cutting lists and fitted furniture. A 12 inch shelf is 304.8mm, but a workshop may round it to 305mm depending on tolerance.
Property & Rooms
Feet are common in listings, but architects and builders usually use metres. A 10ft × 12ft room is about 3.05m × 3.66m.
Roads & Travel
UK road signs commonly use miles and mph. For international travel, 1 mile is 1.609344km and 60mph is 96.56km/h.
Common length conversions
- Inches to millimetres:multiply inches by 25.4. Example: 8 inches × 25.4 = 203.2mm.
- Feet to metres:multiply feet by 0.3048. Example: 6 feet × 0.3048 = 1.8288m.
- Yards to metres:multiply yards by 0.9144. Example: 5 yards × 0.9144 = 4.572m.
- Miles to kilometres:multiply miles by 1.609344. Example: 10 miles × 1.609344 = 16.09344km.
Practical Rounding Tip
For home DIY, round to the nearest millimetre unless you are matching a manufactured component. For structural, glazing, metalwork, cabinetry, pipework and safety-critical work, use the designer’s stated tolerance and do not round without checking the specification.
Weight and Mass Conversion — Ounces, Pounds, Stones and Tons to Metric
Weight conversion in the UK can be confusing because everyday body weight is often expressed in stones and pounds, product packaging is normally metric, gym equipment may show kilograms and pounds, and shipping labels often ask for kilograms. Strictly, the conversion guide is convertingmass, but everyday users usually say “weight”. The most widely used exact factor is1 pound = 0.45359237 kilograms. One ounce is one-sixteenth of a pound, so it equals 28.349523125 grams. One stone is 14 pounds, so it equals 6.35029318 kilograms.
For UK construction and materials, metric tonnes are standard for aggregates, concrete, asphalt, steel and bulk deliveries. An imperial long ton is not the same as a metric tonne. One UK long ton is 1016.0469088kg, while one metric tonne is exactly 1000kg. For older documents, shipping notes or machinery manuals, check whether the text says “ton”, “tonne”, “long ton” or “short ton”. A US short ton is only 907.18474kg, which is a major difference on heavy loads.
- Imperial Weight: 1 ounce; Metric Equivalent: 28.349523125 g; Use Case: Food, postal weight, small items; Rounding Advice: 28.35g or 28g for rough use
- Imperial Weight: 1 pound; Metric Equivalent: 0.45359237 kg; Use Case: Body weight, parcels, gym plates; Rounding Advice: 0.454kg or 454g
- Imperial Weight: 1 stone; Metric Equivalent: 6.35029318 kg; Use Case: UK body weight; Rounding Advice: 6.35kg
- Imperial Weight: 1 long ton; Metric Equivalent: 1016.0469088 kg; Use Case: Older UK/imperial ton; Rounding Advice: Use exact for logistics
- Imperial Weight: 1 short ton; Metric Equivalent: 907.18474 kg; Use Case: US sources; Rounding Advice: Do not confuse with UK ton
Ton vs Tonne Warning
In UK material ordering, a tonne usually means a metric tonne of 1000kg. An imperial long ton is about 1.6% heavier than a metric tonne, while a US short ton is about 9.3% lighter. For aggregates, skip weights, structural steel, crane lifts and vehicle payloads, use the exact unit stated in the supplier document.
Volume Conversion — UK Pints, Fluid Ounces and Gallons to Litres
Volume conversion is where many online guides go wrong for UK users. A UK imperial pint is not the same as a US pint, and a UK imperial gallon is not the same as a US gallon. This page usesUK imperial liquid unitsby default because the page is aimed at UK visitors. One UK gallon equals 4.54609 litres, one UK pint equals 568.26125 millilitres, and one UK fluid ounce equals 28.4130625 millilitres. A US gallon is only 3.785411784 litres, so using the wrong gallon can cause a difference of about 20%.
For recipes, cleaning products, garden chemicals, vehicle manuals, fuel economy, paint coverage and older appliance instructions, always check whether the source is British, American or international. A “cup” in one recipe system may be 240ml, 250ml, or another value. This conversion guide focuses on imperial and metric rather than every cooking convention, but the same principle applies: identify the exact unit first, then convert.
UK Pint
1 UK pint is 568.26125ml. It is larger than a US pint, so recipes and drink references should not be mixed without checking the country.
UK Gallon
1 UK imperial gallon is 4.54609 litres. UK fuel economy in mpg historically uses the imperial gallon, not the US gallon.
Fluid Ounce
1 UK fluid ounce is 28.413ml. US fluid ounces are slightly larger at about 29.574ml, so check imported labels.
UK vs US Liquid Units
Do not use a US gallon for UK mpg, heating-oil references, old British manuals or UK imperial conversion charts. A UK gallon is 4.54609L; a US liquid gallon is 3.785411784L. The names look similar but the result is significantly different.
Area Conversion — Square Feet, Square Yards, Acres and Hectares
Area conversion is important for property, flooring, tiling, landscaping, paint coverage, garden design, land valuation and agricultural references. UK property listings sometimes show floor area in square feet, while architects, surveyors, building control drawings and materials guides often use square metres. One square foot equals 0.09290304 square metres. To convert a room from feet to square metres, convert the full area, not each number roughly in your head unless you are only estimating.
For example, a 12ft by 10ft room is 120 square feet. Multiplying by 0.09290304 gives 11.148 square metres. If you instead round 12ft to 3.7m and 10ft to 3.0m, you get 11.1m², which is close enough for a property description but not always enough for flooring waste, skirting lengths or underfloor heating design. The right level of precision depends on the job.
Area conversions used in UK building and property
- Square inches to square centimetres:multiply by 6.4516.
- Square feet to square metres:multiply by 0.09290304.
- Square yards to square metres:multiply by 0.83612736.
- Acres to hectares:multiply by 0.40468564224.
- Acres to square metres:multiply by 4046.8564224.
Building Material Tip
When converting area for tiles, carpet, laminate, plasterboard, paint, DPM sheets, insulation or paving, always add a waste allowance after the conversion. Common allowances are 5% for simple rectangular areas, 10% for normal rooms, and 15% or more for diagonal cuts, awkward layouts or patterned materials.
More Metric Conversions — Temperature, Speed, Pressure and Practical UK Examples
Some conversions cannot be handled by a simple multiplication factor. Temperature is the best example: Fahrenheit to Celsius needs an offset as well as a scale change. The formula is°C = (°F − 32) × 5 ÷ 9. That means 68°F is 20°C, 86°F is 30°C, and 32°F is 0°C. This is useful for imported appliance manuals, weather reports, oven settings, pool temperatures and American recipe instructions.
Speed conversion is straightforward. Miles per hour multiplied by 1.609344 gives kilometres per hour. UK drivers often encounter mph, while European vehicle data, running apps, cycling computers and international travel guides may use km/h. Pressure conversion appears in tyre pressures, plumbing, heating, gas, HVAC and plant equipment. PSI is common in older or imported equipment, while bar and kilopascals are common in modern metric documentation. One psi is approximately 6.89476 kilopascals.
Temperature
Use the formula because Fahrenheit to Celsius is not just a multiplier. 68°F is 20°C and 212°F is 100°C.
Speed
1 mph equals 1.609344 km/h. A 70mph motorway speed is about 112.65km/h.
Pressure
1 psi equals 6.89476kPa. Many tyre-pressure labels now show both psi and bar/kPa.
Imperial and Metric Units in the UK — 2026 Practical Guidance
The UK uses a mixed measurement culture. Legally and commercially, metric units are widely used as the primary measurement system. Socially and historically, imperial units remain familiar in several everyday settings. Road distances and speed limits are commonly displayed in miles and miles per hour. Beer and cider sold on draught are commonly associated with pints. People often describe height in feet and inches, body weight in stones and pounds, and property sizes in square feet. This is why a UK-focused conversion guide should support both systems clearly.
For businesses, accuracy and presentation matter. GOV.UK guidance for markings and sales says that imperial units may be used voluntarily when selling packaged or loose goods, but metric information must also be displayed and the imperial indication must not be more prominent than the metric measurement. Business Companion guidance from Trading Standards similarly explains that imperial units can be shown as supplementary information but not more prominently than the metric indication. For online content, this means your page can help users understand both systems while still presenting metric values clearly.
For technical work, the safest approach is to use metric as the final specification. If an older plan says a wall is 9 inches, convert it and then check the real on-site dimension, because old buildings may not match modern nominal sizes exactly. If a product is sold as a 4ft sheet, check the manufacturer’s metric dimensions before ordering. If a recipe uses fluid ounces or cups, confirm whether the source is UK or US. Conversion is reliable when the measurement unit is correctly identified; most mistakes come from choosing the wrong unit family.
Authoritative Measurement Sources
The UK National Physical Laboratory explains the International System of Units and the SI base units. NIST publishes detailed SI guidance and conversion factors. UK government and Trading Standards guidance explains when imperial markings may appear alongside metric measurements. This conversion guide uses established conversion factors and explains UK-specific issues such as imperial gallons, stones, miles and supplementary imperial labelling.
How to Use the Imperial to Metric conversion guide Accurately
Start by choosing the measurement category. This matters because a “pound” can mean mass in everyday measurement, but “pound” can also mean money in another context. A “gallon” can mean a UK imperial gallon or a US liquid gallon. A “ton” can mean a UK long ton, a US short ton or a metric tonne. The conversion guide separates categories so the figure remains meaningful.
Next, enter the numeric value. Decimal values are accepted, so you can convert 2.5 inches, 7.75 feet, 1.2 gallons or 0.5 acres. For feet and inches combined, convert each part separately or convert the whole height into inches first. For example, 5ft 10in is 70 inches. Then convert 70 inches to centimetres, which gives 177.8cm. For stones and pounds, convert stones into pounds first by multiplying stones by 14 and adding the remaining pounds. For example, 11st 6lb is 160lb, which is 72.57kg.
Finally, decide how much precision you need. For human-readable web content, rounded values are easier to understand. For technical ordering, keep more decimals or follow the supplier’s tolerances. For example, 1 square foot is exactly 0.09290304m², but flooring pages often display 0.093m². A one-off rounded number is fine for an estimate, but repeated rounding across hundreds of items can create noticeable error.
Identify the Unit
Check whether the source means UK imperial, US customary, metric or a trade nickname before you work out.
Convert with Exact Factors
Use exact definitions for inches, feet, pounds, miles and UK gallons to avoid repeated rounding errors.
Round at the End
Do not round intermediate values if the result will be used for ordering, compliance, fitting or technical work.
Worked Imperial to Metric Examples for Common UK Searches
Search engines often show quick answers for simple conversions, but users still need context when the value is part of a real task. A number alone does not tell you whether to round up, whether UK or US volume was used, whether the result should be written in millimetres or metres, or whether a waste allowance should be added. The examples below explain the working and the practical decision behind it.
Example 1: 6 feet to metres and centimetres
Six feet is a common height conversion. Since 1 foot is exactly 0.3048 metres, 6 feet equals 1.8288 metres. In centimetres, that is 182.88cm. For personal height, it is normal to write this as approximately 183cm. For a doorway, wardrobe, shower screen or fitted panel, you should not simply use 183cm unless the design tolerance allows it; keep the exact millimetre equivalent and verify the measured opening.
Example 2: 10 feet by 12 feet room to square metres
A room measuring 10ft by 12ft has an area of 120 square feet. One square foot equals 0.09290304m², so the room is 11.1483648m². A property listing may round this to 11.1m², while a flooring order might round to 11.15m² and then add 5% to 10% for waste. If the room is not perfectly rectangular, measure each section separately in metres and add them together.
Example 3: 1 UK gallon to litres
One UK imperial gallon equals 4.54609 litres. This is the correct gallon for traditional UK miles-per-gallon fuel economy and many older British references. If a source is American, 1 US liquid gallon equals 3.785411784 litres instead. A fuel economy figure of 40 mpg means a different litres-per-100km value depending on whether the gallon is UK or US, so always identify the country of the source before converting.
Example 4: 11 stone 6 pounds to kilograms
Convert stones into pounds first. Eleven stones is 154 pounds. Add the extra 6 pounds to get 160 pounds. Multiply 160 by 0.45359237 to get 72.5747792kg. For everyday body weight, this is usually shown as 72.6kg or 73kg, but for sport, medical or fitness tracking, use the precision required by the app or professional guidance.
Example 5: 70 mph to km/h
One mile per hour equals 1.609344 kilometres per hour. Therefore, 70mph equals 112.65408km/h. This is often rounded to 113km/h. When comparing UK and European road speeds, remember that speed limits are legal limits in the units displayed locally; do not rely only on a rough mental estimate when driving.
SEO and User Experience Tip
For conversion pages, give both the exact result and the practical result. Users who need a quick answer can read the rounded value, while builders, students, engineers, designers and ecommerce users can still see the exact conversion factor.
Imperial to Metric Formulas You Can Use Manually
The guide is fastest, but formula lists are useful for students, website writers, tradespeople, spreadsheet users and anyone building product descriptions. These formulas use standard conversion factors and can be copied into spreadsheets, guides or content briefs. For simple multiplication units, multiply the imperial value by the metric factor. For temperature, use the full Fahrenheit-to-Celsius formula because the zero points of the scales are different.
- Inches to millimetres:mm = inches × 25.4
- Feet to metres:m = feet × 0.3048
- Yards to metres:m = yards × 0.9144
- Miles to kilometres:km = miles × 1.609344
- Ounces to grams:g = ounces × 28.349523125
- Pounds to kilograms:kg = pounds × 0.45359237
- Stones to kilograms:kg = stones × 6.35029318
- UK pints to litres:L = UK pints × 0.56826125
- UK gallons to litres:L = UK gallons × 4.54609
- Square feet to square metres:m² = sq ft × 0.09290304
- Acres to hectares:ha = acres × 0.40468564224
- Fahrenheit to Celsius:°C = (°F − 32) × 5 ÷ 9
When adding these formulas to a web page, avoid mixing too many unit styles in one sentence. A clean page should define the imperial measurement, show the metric figure, and then explain the real-world use case. For example, instead of writing “10ft is 3.048m or 304.8cm or 3048mm” everywhere, choose the unit that fits the context. Room sizes usually work best in metres, small product dimensions usually work best in millimetres, and personal height usually works best in centimetres.
Use Metric Values for Final Specifications
This imperial to metric guide is designed for fast, practical conversion. For building control drawings, manufactured components, labelling, safety data, product compliance or engineering work, always confirm the required unit, tolerance and standard before ordering or publishing final figures. See theFAQfor common UK conversion mistakes.
Imperial to Metric conversion guide — Frequently Asked Questions
Common questions about UK imperial units, metric equivalents, rounding and conversion accuracy in 2026.
The easiest method is to choose the correct measurement category and multiply by the accepted conversion factor. Inches convert to millimetres by multiplying by 25.4, feet convert to metres by multiplying by 0.3048, pounds convert to kilograms by multiplying by 0.45359237, and UK gallons convert to litres by multiplying by 4.54609. This resource does those working automatically and shows practical rounding guidance.
Yes. The international inch is defined as exactly 25.4 millimetres, which is exactly 2.54 centimetres. This makes inch-to-metric conversion reliable for technical use. The practical question is how many decimals you keep after converting. For most DIY measurements, nearest millimetre is fine; for precision manufacturing, use the specified tolerance.
Convert the feet into inches, add the remaining inches, then multiply by 2.54. For example, 5ft 10in is 5 × 12 + 10 = 70 inches. Then 70 × 2.54 = 177.8cm. You can also convert feet to metres and inches to centimetres separately, but combining into total inches first is usually simpler.
Multiply stones by 14 to convert them to pounds, add any extra pounds, then multiply the total by 0.45359237. For example, 12st 4lb is 172lb. Multiplying 172 by 0.45359237 gives 78.02kg. This is useful for UK body weight, health records and fitness tracking.
No. A UK imperial gallon is 4.54609 litres. A US liquid gallon is 3.785411784 litres. The difference is large enough to affect fuel economy, recipes, chemical dilution, aquarium sizing and equipment manuals. For UK mpg, older UK manuals and British references, use the imperial gallon unless the source clearly says US gallon.
One square foot equals 0.09290304 square metres. To convert square feet to square metres, multiply by 0.09290304. For example, 500 sq ft equals 46.45152m². For property listings, this may be rounded to 46.5m². For flooring and materials, add waste allowance after converting.
One acre equals 4046.8564224 square metres. It is also equal to about 0.404686 hectares. Acres are still common in UK land, garden, farm and property descriptions, while hectares and square metres are used for many technical and planning documents.
For many sales contexts, UK guidance expects metric measurements to be shown. Imperial units may be used voluntarily as supplementary information, but the metric value must be displayed and imperial information must not be more prominent. This is why product labels often show grams, kilograms, millilitres or litres first, with imperial equivalents sometimes shown second.
Round only when the project tolerance allows it. For rough estimating, nearest millimetre, centimetre or 0.1m² may be fine. For manufactured parts, glazing, structural steel, cabinets, pipework, insulation boards, DPM laps and compliance drawings, keep the precise converted value and follow the supplier’s or engineer’s tolerance.
Mass is the amount of matter in an object and is measured in kilograms in the SI system. Weight is a force caused by gravity. Everyday speech uses “weight” for body weight, parcels and materials, so guides often say weight even when converting mass units like pounds to kilograms. For normal everyday conversion on Earth, this is acceptable, but scientific and engineering contexts may distinguish the terms more carefully.
Yes, for units that are the same internationally, such as inches, feet, yards, miles and pounds. Be careful with liquid volume. UK and US gallons, pints and fluid ounces are different. The guide includes UK imperial volume units and US liquid gallon/pint/fluid ounce options so you can select the correct source unit.
Differences usually come from rounding, using US volume instead of UK imperial volume, or converting through an intermediate rounded value. The exact relationship for many units is fixed, but websites may display fewer decimal places. For technical work, use exact factors and round at the final step only.
Related UK Guides and Reference Guides
Use these related resources with your imperial to metric conversions for building, estimating, materials and UK specification work.