Convert between everyday units: length, weight, temperature, area, volume, speed and time — miles to kilometres, Fahrenheit to Celsius, gallons to litres and plenty more, with the conversion factor shown.
Conversion Calculator
How the Conversion Calculator Works
The Conversion Calculator changes a value from one unit to another. It covers seven categories: length, weight, temperature, area, volume, speed (meters per second, kilometers per hour, miles per hour, and knots), and time. Choose a category first, then pick units from the matching lists. A single page handles the most common conversions, so a recipe in cups, a road distance in miles, a temperature in Fahrenheit, or a parcel weight in pounds can all be expressed in the unit you need. It is the tool for cooking, travel, schoolwork, online shopping, and any document that mixes imperial and metric measurements.
Each conversion uses a fixed factor or, for temperature, a fixed formula. A mile is 1.60934 kilometres, a kilogram is 2.20462 pounds, and a litre is 0.264172 US gallons. To convert, the calculator multiplies the value by the factor that takes it from the chosen unit to the target unit, so converting in the other direction divides by the same factor. Temperature needs a formula rather than a single factor: Fahrenheit to Celsius is (value − 32) × 5/9, Celsius to Fahrenheit is (value × 9/5) + 32, and Kelvin is Celsius plus 273.15. Area and volume conversions square or cube the length factor, which is why a square mile is far more than 1.60934 square kilometres.
This calculator implements each conversion with the standard factor for that pair, and results are rounded to a sensible number of decimal places for display. Because conversion factors are exact definitions or internationally agreed values, results are reliable to the precision shown. One caution is units that share a name but not a value: the US gallon and the imperial gallon are different, so this calculator uses US gallons for volume, and the result is labelled as such. Always check which gallon, ton, or pint a source means before converting a large quantity.
How to Use This Calculator
- Choose the category you need: length, weight, temperature, area, volume, speed, or time.
- Enter the value you want to convert in the value field.
- Select the unit you are converting from in the first dropdown.
- Select the unit you are converting to in the second dropdown.
- Press Convert to run the calculation.
- Read the converted result, and note the reverse conversion if the calculator shows it.
Example
For a tested example, convert 100 degrees Fahrenheit to Celsius. The formula is (100 − 32) × 5/9 = 68 × 5/9 = 37.78. So 100 °F is 37.78 °C, which is just above normal body temperature. As a check, 0 °C is 273.15 K, so the same method extends to Kelvin by adding 273.15 to the Celsius figure.
As a second example, convert 5 kilometres to miles. The factor is 1 mile = 1.60934 kilometres, so the conversion divides: 5 ÷ 1.60934 = 3.107. So 5 km is about 3.107 miles. A second check with time shows the same idea in a simpler form: 2 hours is 120 minutes, because the factor is 60 minutes per hour.
Understanding Your Result
The converted value is the same quantity expressed in a different unit, so it should feel plausible: converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller number. If the result looks wildly wrong, the most likely cause is a swapped from and to unit, which inverts the factor and gives a very different answer. For temperature, a negative result is normal for cold values in Celsius or Fahrenheit, and Kelvin can never be negative, because absolute zero is 0 K.
Rounding is for display, not for the underlying value. A result shown as 3.107 miles from 5 kilometres is accurate to three decimal places, and converting it back gives 5.000 kilometres within the displayed precision. For very large or very small quantities, check the unit label carefully: confusing US and imperial gallons, or short tons and metric tonnes, changes the answer even when the number looks reasonable.
Conversion Calculator FAQs
Why does temperature need a formula instead of a factor?
Because the Fahrenheit and Celsius scales start at different points as well as using different step sizes. A factor alone cannot shift the zero point, so the conversion must subtract 32 before scaling, or add it after.
What is the difference between US and imperial gallons?
The US gallon is 3.785 litres and the imperial gallon is 4.546 litres, so they are not interchangeable. This calculator uses US gallons for volume conversions, and the result is labelled accordingly.
Can I convert between units in different categories?
No, length can only convert to length, weight to weight, and so on. Converting miles to kilograms has no meaning, because the quantities measure different things.
How precise are the results?
Conversion factors are standard definitions or internationally agreed values, so results are reliable to the precision shown. Rounding only affects the displayed digits, not the underlying calculation.
Why does converting back not always give the exact original number?
Because the displayed result is rounded, converting it back can differ by a tiny amount in the last decimal place. The underlying calculation is exact, but the rounded display loses a little precision.
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