Written by Sarah Mitchell · Reviewed by Alex Chen · July 17, 2026
Convert between units of length, weight, volume, temperature, speed, area, and pressure.
Enter a value and click Convert.
Most of the world measures distance in kilometers while a few countries still post road signs in miles, so the same run, drive, or parcel can be described two completely different ways. This converter spans seven categories — length, weight, volume, temperature, speed, area, and pressure — and translates any value in one category into any other unit in that same category. The conversion factors are fixed constants baked into the page, and the arithmetic happens locally, so nothing you enter is transmitted anywhere.
A runner who wants the metric version of a familiar 5-mile route can convert it in one step. The mile-to-kilometer factor is 1.609, so 5 miles is 5 × 1.609 = 8.045 kilometers, which the tool displays as 8.05 km after rounding to two decimals. The same value expressed in meters is 8,045, and in centimeters it is 804,500, so the category dropdowns make every scale available without re-entering the number.
Most categories multiply by a fixed factor, but temperature uses an offset as well. Celsius to Fahrenheit follows F = C × 9/5 + 32, so 25 °C becomes 77 °F: multiply 25 by 9/5 to get 45, then add 32. Going the other way, (F − 32) × 5/9, turns 98.6 °F into exactly 37 °C. Kelvin plugs into the same chain through Celsius, with the 273.15 offset applied at the edges.
Internally, every category is anchored to one base unit, so a conversion between two unusual units never needs a direct formula of its own. Both sides are expressed in the base unit first, then scaled out again, which keeps the result identical regardless of which direction you convert. For example, converting 2 kilograms to pounds routes the value through grams and arrives at 4.41 lb, the same figure a direct factor would produce.
Results are rounded to six decimal places internally and trimmed for display, so everyday figures like 8.05 km come out clean. Volume units follow US customary definitions, meaning a US gallon differs from a UK imperial gallon — if you are cooking with imperial measures, the dedicated cooking converter is the better fit. For temperature, the exact SI formulas are used, so a converted reading can be trusted for lab work as well as for deciding what to wear.
This page was last reviewed in June 2026, when the conversion factors were rechecked against the current SI definitions and the unit lists were refreshed. Keeping the constants current matters because a stale factor drifts into visible errors at six decimal places. No input data is ever collected, and the page keeps working with the network disconnected once it has loaded.
Speed is one of the most common real-world conversions. Sixty miles per hour equals about 96.6 kilometers per hour, and to reverse the direction you divide by the same 1.609 factor. The United States and the United Kingdom post road limits in miles per hour while most other countries use kilometers per hour, so a quick conversion keeps a rental car on the legal side of a foreign speed limit.
Some of the most expensive mix-ups come from units that look alike but are not. A fluid ounce measures volume while an ounce measures weight, so a recipe calling for 8 ounces of flour and 8 fluid ounces of milk is asking for two different quantities. A stone equals 14 pounds and still describes body weight in the United Kingdom, while Americans see the same figure in pounds. Pressure shows up as psi in tire shops, bar on scuba gear, and kilopascals in engineering reports, all measuring the same inflation with different scales. Land records use hectares in most of the world but acres in the United States, and the 2.471 factor converts one to the other. Keeping the category straight before converting is half the battle, because a number means nothing without the unit attached to it.