Metric to Imperial Conversion Chart: Length, Weight, Volume & Temperature
A recipe says 350°F. Your European oven says 175°C. The road sign says 60 mph, the rental car's speedometer reads km/h, and the package label lists both pounds and kilograms. The world runs on two measurement systems, and most of us trip over the boundary between them regularly. This guide covers where each system came from, the conversions you'll actually use, and which countries still hold out. For instant answers, use our length converter and weight converter.
A Short History of Two Systems
The imperial system grew organically out of medieval English trade: an inch was roughly a thumb's width, a foot a human foot, a mile a thousand Roman paces. It was practical for its time but chaotic — units related to each other by awkward numbers like 12, 16 and 5,280. The metric system was born in revolutionary France in the 1790s as a deliberate, rational alternative: one meter defined from the Earth's circumference, with everything else in clean powers of ten. It spread with trade and science until, by the late 20th century, nearly the entire world had officially adopted it.
The United States is the famous exception. Congress legalized metric use as early as 1866, and the 1970s brought a genuine push to convert — but the effort was voluntary, industry balked at the cost of retooling, and the campaign fizzled. American science, medicine and the military went metric; American daily life stayed imperial.
Who Uses What in 2026
Only three countries have never officially adopted the metric system: the United States, Liberia and Myanmar. Everyone else is officially metric — but "officially" hides a lot of everyday mixing. The UK is the champion of the hybrid: road distances in miles, beer in pints, body weight in stones and pounds, yet food sold in grams and temperature debated in both Celsius and Fahrenheit. Canada is officially metric but still quotes heights in feet and inches and oven temperatures in Fahrenheit in casual conversation. The result: if you travel or shop internationally, you will meet both systems no matter where you go.
The Conversions You'll Actually Use
| Convert | Multiply by | Example |
|---|---|---|
| Miles → kilometers | 1.609 | 60 mph ≈ 97 km/h |
| Kilometers → miles | 0.621 | 10 km ≈ 6.2 miles |
| Pounds → kilograms | 0.454 | 150 lb ≈ 68 kg |
| Kilograms → pounds | 2.205 | 70 kg ≈ 154 lb |
| Inches → centimeters | 2.54 | 32 in TV ≈ 81 cm |
| Feet → meters | 0.3048 | 6 ft ≈ 1.83 m |
| Fluid ounces → milliliters | 29.57 | 8 fl oz cup ≈ 237 ml |
| Gallons (US) → liters | 3.785 | 15 gal tank ≈ 57 L |
For temperature there is no single multiplier — use the formulas: °F = (°C × 9/5) + 32, and °C = (°F − 32) × 5/9. The handy anchors: 0°C = 32°F (freezing), 20°C = 68°F (room temperature), 37°C = 98.6°F (body temperature), 100°C = 212°F (boiling).
Why It Still Matters
Mixing systems has real consequences. The most famous: in 1999 NASA lost the $125 million Mars Climate Orbiter because one team used metric newtons and another used imperial pound-force. Closer to home, medication doses, engineering parts, cooking measurements and luggage allowances all punish conversion errors. The practical rule is simple: know which system your source uses, convert deliberately rather than guessing, and when precision matters — medicine, engineering, baking — use a converter instead of mental math.
The Conversions That Catch People Out
Most conversion errors are not arithmetic errors — they are unit traps, where the same word means two different amounts:
Two gallons. A US gallon is 3.785 litres; an imperial (UK) gallon is 4.546 litres — about 20% bigger. Fuel economy figures, paint coverage and aquarium sizes all change depending on which gallon the source means, and UK and US sources rarely say.
Two kinds of ounce. The ounce on a kitchen scale (28.35 g, weight) and the fluid ounce in a measuring jug (29.57 ml US, volume) are different units that share a name. They only coincide for water; for flour, honey or oil they diverge fast.
Ton, tonne and long ton. A US (short) ton is 2,000 lb = 907 kg. A tonne is 1,000 kg = 2,204.6 lb. A British long ton is 2,240 lb = 1,016 kg. Shipping and construction quotes that just say "tons" deserve one clarifying question.
Miles that are not miles. A nautical mile is 1.852 km, not the 1.609 km of a land mile — which is why ship and aircraft speeds in knots never convert the way travellers expect. Our length converter handles the everyday units side by side so you can see the difference before it costs you.
Unit fluency shows up in unlikely places — including export settings, where a living-photo loop is sized in pixels, inches or centimetres depending on the platform asking. The Cinemagraph Maker turns a short video into one of those loops: paint the moving region, freeze the rest, export.
Frequently Asked Questions
Which countries still use the imperial system?
Why does the US use imperial instead of metric?
How do I convert miles to kilometers?
What is the difference between metric and imperial?
Why is a US gallon smaller than a British gallon?
Is a ton the same as a tonne?
More guides from ToolNest
KG to LBS: How to Convert Kilograms, Pounds, Stone and Ounces
The exact kg factors for six units, a 12-stone worked example (= 76.20 kg, 168 lb), the stone explained, and the two-ton and two-ounce traps.
Celsius to Fahrenheit: The Conversion Formulas, Reference Points and Mental Shortcuts
°F = °C × 9/5 + 32 explained — a 180°C recipe and a 115°F heatwave worked in full, anchor points like 37°C = 98.6°F, and when the double-and-add-30 shortcut is safe.
USD to EUR Conversion: How Exchange Rates and Fees Really Work
Mid-market rates vs the rate you actually get, hidden markups, and how to check the real cost before you convert.