Unit Converter takes a plain-language query like 5 km to miles or 98.6f to c and converts it exactly, using Fraction.js to keep every intermediate step a rational number instead of a rounded floating-point approximation.
No dropdowns, no unit picker to scroll through. Type an amount, a unit, the word “to” (or “in” or “zu”), and the target unit, and the result appears as you type.
How It Works
Every unit is a node in a graph, and every known relationship between two units is an edge. Converting in to mm means finding a path through the graph, for example in → cm → mm, and multiplying the conversion factors along that path. The tool shows this path underneath the result, so you can see exactly how the number was derived instead of trusting a black box.
Almost every edge is a plain multiplication (1 inch is always 2.54 cm, no matter the direction), but temperature scales are not: 0°C is not 0°F. Celsius, Fahrenheit, and Kelvin are stored as affine transforms, y = m·x + c, and the tool composes those transforms along the path the same way it composes plain ratios, so a Fahrenheit-to-Kelvin conversion is quietly routed through Celsius under the hood.
Every conversion factor that has an exact definition, an inch is exactly 2.54 cm, a pound is exactly 0.45359237 kg, a nautical mile is exactly 1852 m, is stored as a string and parsed by Fraction.js's exact decimal parser rather than passed through a floating-point division first. That is why the tool can tell you a result is exact and mean it: whenever the resulting fraction has a denominator other than 1, it is shown underneath the decimal value.
How to Use It
- Type an amount, a unit, a connector word (
to,in, orzu), and the target unit:5 km to miles. - The amount can be omitted if you just want a 1:1 comparison:
km to miles. - Fractions work directly:
3/4 cup to ml. - Powers of two are handy for data sizes:
2^10 bit to kb. - Negative numbers work, which matters for temperature:
-40 f to c. - Both
.and,are accepted as the decimal separator. - Unit spelling is case-insensitive, and most units accept plurals, symbols, and common alternative spellings (
ft,foot,feet, and'are all the same unit).
Example Inputs
5 km to miles98.6f to c— body temperature, Fahrenheit to Celsius3/4 cup to ml— a recipe measurement2 stone to kg1 gb to mb— binary (1024-based) conversion60 mph to km/h1 au to km— astronomical distance1 atm to psi-40 c to f— the one temperature where both scales agree
Supported Units by Category
Every category below is fully connected: any unit can be converted to any other unit in the same category. Units in different categories, for example kg and km, cannot be converted into each other, and the tool will tell you so instead of guessing.
Length
km, hm, dam, m, dm, cm, mm, um (micrometer, also µm), nm (nanometer), pm (picometer), angstrom (Å), mi (mile), yd (yard), ft (foot, '), in (inch, "), fathom, furlong, chain, mil (thou), nmi (nautical mile, sm), au (astronomical unit), ly (light-year), pc (parsec).
Mass
kg, g, mg, ug (microgram), t (tonne), lb (pound), oz (ounce), grain, stone, ton (US short ton), longton (UK long ton), carat.
Volume
m3, l, hl, dl, cl, ml, cm3/cc, gal (US gallon), quart, pint, cup, floz (fluid ounce), tbsp (tablespoon), tsp (teaspoon), ukgal (imperial gallon).
Area
km2, m2, cm2, mm2, ha (hectare), acre, ft2, in2, yd2, mi2.
Speed
m/s, km/h, mph, ft/s, knot.
Rotation / Angle
deg (°), rad, rev (revolution, turn), grad (gradian, gon), rpm, rad/s.
Time
ns, us (µs), ms, s, min, h, day, week, year (365.25 days, the Julian average).
Temperature
c (Celsius), f (Fahrenheit), k (Kelvin).
Digital Storage
bit, b (byte), kb, mb, gb, tb, pb. These follow the 1024-based binary convention (1 kb = 1024 b), the same one operating systems use for file sizes, not the 1000-based SI convention some standards bodies prefer for KiB/MiB.
Energy
j (joule), kj, cal (calorie), kcal, wh (watt-hour), kwh, btu.
Power
w (watt), kw, hp (horsepower, also ps).
Pressure
pa (pascal), kpa, bar, atm, psi, mmhg (also torr).
Frequency
hz (hertz), khz, mhz, ghz.
Notes on Precision
Most conversion factors used here are exact by international definition, not rounded measurements: the inch, the pound, the nautical mile, the international calorie, and the astronomical unit all have an exact legal value in SI units. Where a conversion is genuinely irrational, converting radians to degrees involves π, the tool uses a double-precision decimal approximation and the result is shown as a decimal only, without a false claim of exactness.
The Julian year used for year (365.25 days) is an average; calendar years are 365 or 366 days depending on leap years, so conversions involving year are intentionally approximate over long spans.