Use this free unit converter to switch between measurements in six categories: length, weight (mass), temperature, area, volume and speed. Choose a category, select the source and target units, and type a value to see the converted result. Common examples include miles to kilometers, pounds to kilograms, Celsius to Fahrenheit, US liquid gallons to liters and knots to kilometers per hour. The converter uses defined physical-unit relationships rather than rough mental estimates, and shows up to ten significant digits without rounding intermediate values. There are no currency exchange rates, account requirements or subscription fees.
## Length: meters, feet, miles and nautical miles. Metric length conversions use powers of ten. One kilometer is 1,000 meters and one centimeter is 0.01 meter. Under the international definition, one inch is exactly 0.0254 meter, one foot is exactly 0.3048 meter and one international mile is exactly 1,609.344 meters. A nautical mile is exactly 1,852 meters, so it is longer than an international land mile. For example, five international miles convert to 5 × 1.609344 = 8.04672 kilometers. The U.S. survey foot is a separate historical definition; this converter uses the modern international foot.
## Kilograms, pounds, ounces and stone. The Weight category converts conventional units of mass. One international avoirdupois pound is exactly 0.45359237 kilogram. One ounce is one-sixteenth of that pound, or 0.028349523125 kilogram; one stone is fourteen pounds, or 6.35029318 kilograms. Therefore, 70 kilograms correspond to approximately 154.32358 pounds. The tool uses the unit definitions directly and does not round the conversion ratio to 2.2. A scale may itself have a different measurement tolerance, so more displayed digits do not mean the original measurement is more accurate.
## Temperature uses a different kind of formula. Converting Celsius to Fahrenheit requires both a multiplier and an offset: °F = (°C × 9/5) + 32. The reverse is °C = (°F − 32) × 5/9. For example, 25°C is exactly 77°F, and 0°C is 32°F. The Kelvin scale uses K = °C + 273.15, so 0°C is 273.15 K. It is physically invalid to enter a temperature below absolute zero. The converter rejects such inputs instead of returning a nonsensical negative Kelvin temperature. Kelvin is written without a degree symbol.
Physical unit factors and temperature formulas
Target value = Source value × (Source-to-base factor ÷ Target-to-base factor)
°F = (°C × 9/5) + 32
°C = (°F − 32) × 5/9
K = °C + 273.15
1 mi = 1.609344 km
1 lb = 0.45359237 kg
1 US liquid gal = 3.785411784 L
For length, mass, area, volume and speed, use fixed factors relative to a common base unit. Temperature is handled using additive offsets and a scale. Inputs below absolute zero are rejected. The displayed output is rounded for readability, not used for intermediate calculations.
Convert 25 degrees Celsius into Fahrenheit and 70 kilograms into pounds.
Result: 25°C = 77°F, and 70 kg ≈ 154.32358 lb.
One international mile is exactly 1.609344 kilometers. Five miles convert to 8.04672 km. This is the international mile, not the historical U.S. survey mile.
Divide kilograms by 0.45359237 because one avoirdupois pound is exactly 0.45359237 kg. For 70 kg, the result is approximately 154.32358 lb.
Multiply Celsius by 9/5 and add 32. For example, 25°C = 77°F. To reverse the conversion, subtract 32 from Fahrenheit and multiply by 5/9.
One U.S. liquid gallon is exactly 3.785411784 liters. This conversion does not use imperial gallons or dry gallons.
Multiply knots by 1.852 because one knot is one nautical mile per hour and a nautical mile is exactly 1,852 meters.
No. Celsius and Fahrenheit differ by both an offset and a scale. Kelvin is an absolute scale and cannot physically be negative.
Length, weight (mass), temperature, area, volume and speed. Digital storage, pressure, energy, currency and time are not offered in this particular tool.
The tool displays up to ten significant digits from the fixed conversion calculation. The accuracy of a measurement is still limited by the quality and precision of the input value.