Unit Converter — Convert Length, Weight, Temperature & More
Type a number, pick your units, get the conversion instantly. Covers length, weight, temperature, area, volume, and speed. Metric ↔ imperial, with the exact conversion factor shown so you can verify. Runs in your browser.
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Easily convert between different units: Length
Easily convert between different units
Supported conversions:
- Length: Metric (m, km, cm, mm) and Imperial (mi, yd, ft, in)
- Weight: Metric (kg, g, mg) and Imperial/US (lb, oz)
- Temperature: Celsius, Fahrenheit, Kelvin
- Area: Square meters, square feet, acres, hectares
- Volume: Liters, gallons, quarts, cups
- Speed: m/s, km/h, mph, knots
How Unit Conversion Works
Most unit conversions are simple multiplication: 1 mile = 1.60934 km, so multiply miles by 1.60934 to get kilometers. The tool stores precise conversion factors (not rounded approximations) and chains them when needed — converting feet to centimeters goes through meters internally.
Temperature is the exception. Celsius, Fahrenheit, and Kelvin don't share a zero point, so you can't just multiply. The formulas: °F = °C × 9/5 + 32. K = °C + 273.15. That +32 offset is why temperature conversion feels different from everything else.
Precision note: we display up to 6 significant digits. For everyday use (cooking, travel, fitness) that's more than enough. For scientific or engineering work requiring 15+ digits of precision, use a dedicated library like Python's pint or GNU Units — browser floating-point math has inherent limitations around the 15th decimal place.
Common confusion: "metric ton" (1000 kg) vs "short ton" (2000 lb ≈ 907 kg) vs "long ton" (2240 lb ≈ 1016 kg). Similarly, a US gallon (3.785 L) is different from an Imperial gallon (4.546 L). This tool labels units clearly to avoid these mix-ups.
How to Use
- Select the category: length, weight, temperature, area, volume, or speed.
- Enter your value in the input field.
- Choose source and target units from the dropdowns.
- Result appears instantly with the conversion factor shown below.
When You'll Use This
Traveling between metric and imperial countries
Speed limits in km/h vs mph, distances in kilometers vs miles, temperatures in Celsius vs Fahrenheit. Quick conversions without mental math — is 35°C hot? (Yes, it's 95°F.)
Cooking with recipes from different countries
American recipes use cups and Fahrenheit, European ones use grams and Celsius. Convert 350°F to °C (177°C), or figure out how many grams are in 2 cups of flour (about 240g, but that depends on the ingredient — this tool handles the unit math, you handle the density).
Fitness and health tracking across systems
Your scale shows kg but the app wants lbs. You ran 5 km but want to log miles. Your height is 175 cm but the form asks for feet and inches (5'9"). Quick conversions without googling each time.
Engineering and construction calculations
Working with international specs that mix metric and imperial. Convert square meters to square feet for flooring, liters to gallons for tank capacity, or meters per second to km/h for machinery specs.
Things to Know
Temperature is not proportional — don't multiply
20°C is not "twice as hot" as 10°C (that would be 283K vs 293K — barely different in absolute terms). And 0°F is not "zero heat." Temperature scales have arbitrary zero points. Always use the formula, never multiply/divide temperatures.
US vs Imperial gallons — they're different
A US gallon is 3.785 liters. An Imperial (UK) gallon is 4.546 liters — about 20% larger. If a British car manual says "5 gallon tank" and you fill with US gallons, you'll overflow. This tool labels them separately.
Square and cubic units don't scale linearly
1 meter = 3.281 feet, but 1 square meter = 10.764 square feet (3.281²), and 1 cubic meter = 35.315 cubic feet (3.281³). People often forget to square/cube the conversion factor for area and volume.
Nautical miles are not regular miles
A nautical mile is 1.852 km (based on one minute of latitude). A statute mile is 1.609 km. Aviation and maritime use nautical miles; everything else uses statute miles. Don't mix them up when reading charts.
Examples
Marathon distance in miles
A marathon is 42.195 km — how far is that in miles?
Input
42.195 kmOutput
26.219 miles (the classic 26.2)Body temperature in Fahrenheit
Normal body temperature is 37°C — what's that in Fahrenheit?
Input
37 °COutput
98.6 °FFeatures
- Six categories: length, weight, temperature, area, volume, speed
- Metric and imperial units with precise conversion factors
- Shows the conversion rate so you can verify the math
- One-click swap between source and target units
- Handles scientific notation for very large/small values
- Runs 100% in your browser — no data sent anywhere
Frequently Asked Questions
Why does temperature conversion use a formula instead of a simple ratio?
Because Celsius, Fahrenheit, and Kelvin have different zero points. 0°C is the freezing point of water, 0°F is an arbitrary point (originally the coldest temperature Fahrenheit could create in his lab), and 0K is absolute zero. You can't convert between them by multiplying — you need the offset formula: °F = °C × 9/5 + 32.
What's the difference between a US gallon and an Imperial gallon?
A US gallon is 3.785 liters, an Imperial (UK) gallon is 4.546 liters — about 20% larger. This also affects related units: a US fluid ounce is 29.57 mL, an Imperial fluid ounce is 28.41 mL. When converting, always check which gallon system is being used.
How do I convert square meters to square feet?
Multiply by 10.764. The linear conversion is 1m = 3.281ft, but for area you square it: 3.281² = 10.764. So a 50m² apartment is about 538 sq ft. Common mistake: using 3.281 instead of 10.764 for area conversions.
Is a "ton" always the same?
No. A metric ton (tonne) = 1000 kg. A US short ton = 2000 lb ≈ 907 kg. A UK long ton = 2240 lb ≈ 1016 kg. In international trade, "ton" usually means metric ton. In US domestic contexts, it usually means short ton. Always clarify which ton is meant.
Why do my conversions show slight rounding differences from other tools?
Different tools use different precision levels for conversion factors. We use the internationally agreed values (e.g., 1 inch = exactly 25.4 mm, 1 pound = exactly 0.45359237 kg). Small differences in the last decimal places come from rounding at different steps. For everyday use, these differences are negligible.
Tips & Related Workflows
- Converting currencies instead of units? Use our Currency Converter.
- Calculate BMI after converting your height and weight with our BMI Calculator.
- Need percentage calculations for unit ratios? Try our Percentage Calculator.
- Do complex scientific conversions with our Scientific Calculator.