How do I convert units online for free?

Type your value, pick a category (length, weight, temperature, or volume), enter the from and to units, and run the tool — the conversion is computed instantly in your browser with no signup and no cost.

How do I use a length converter for km to miles?

Select the Length category, type km in "From unit" and miles in "To unit", then run the tool. For example, 100 km converts to 62.1371 miles using the standard 1 mile = 1.609344 km factor.

How do I convert weight from kg to lbs?

Select the Weight category, enter kg as the from unit and lbs as the to unit. The tool converts through the exact kilogram–pound factor (1 kg = 2.20462 lbs), so 70 kg becomes about 154.32 lbs.

How do I convert temperature from Celsius to Fahrenheit?

Select the Temperature category and enter celsius and fahrenheit. Temperature uses real formulas, not simple factors — 100 °C becomes 212 °F via °F = (°C × 9/5) + 32.

How do I convert between metric and imperial units?

Pick the matching category, then type any metric unit (km, kg, liters) and any imperial unit (miles, lbs, gallons) — the tool converts between the systems automatically, e.g. 1 US gallon = 3.7854 liters.

Unit Converter — Length, Weight, Temperature & Volume

What is Unit converter?

Unit Converter — Convert units online free — length, weight, temperature and volume with accurate formulas. Metric to imperial instantly: km to miles, kg to lbs, °C to °F.

Conversions are computed by the unitfyi open-source engine (FYIPedia unitfyi-js, MIT): linear unit pairs convert through per-unit factors against a base unit, and temperature uses proper function-based formulas (°F = (°C × 9/5) + 32, K = °C + 273.15, and equivalents). Results are smart-rounded by the engine for readability. Unit names are matched against the engine's own alias tables, so km, kilometre, and kilometres all resolve to the same unit. Limitation: an unrecognized unit name returns an error listing the valid units for that category rather than guessing.

Why use this unit converter?

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Built for unit converter

Convert units online free — length, weight, temperature and volume with accurate formulas. Metric to imperial instantly: km to miles, kg to lbs, °C to °F.

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Transparent & honest

Unit names must match the engine's known units or aliases (km, kilometre, miles all work); anything else returns a friendly error listing the valid units.

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Private by design

Everything runs in your browser. Your inputs never leave your device.

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Works everywhere

Fully responsive — perfect on desktop, tablet, and mobile. No app needed.

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Regularly updated

Regularly maintained and reviewed to ensure accuracy.

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Free forever

No accounts, no limits, no watermarks. Use Unit Converter as much as you need.

How to use Unit Converter

1Type the number you want to convert into the "Value" field.
2Pick a "Category": Length, Weight, Temperature, or Volume.
3Type the unit you are converting from in "From unit" — e.g. km, lbs, or °C.
4Type the unit you are converting to in "To unit" — e.g. miles, kg, or °F.
5Run the tool to get the converted result instantly, free with no signup.

What can you do with Unit Converter?

Convert units online free — Convert units online free — length, weight, temperature and volume with accurate formulas.
Length converter km to miles — Convert units online free — length, weight, temperature and volume with accurate formulas.
Convert weight kg to lbs — Convert units online free — length, weight, temperature and volume with accurate formulas.
Convert temperature celsius to fahrenheit — Convert units online free — length, weight, temperature and volume with accurate formulas.
Convert metric to imperial units — Convert units online free — length, weight, temperature and volume with accurate formulas.

Good to know

Unit names must match the engine's known units or aliases (km, kilometre, miles all work); anything else returns a friendly error listing the valid units.
Results are rounded by the engine for readability — fine for everyday use, but use a scientific calculator when you need full precision.
Temperature conversions use standard formulas; linear conversions use fixed factors that do not account for relativistic or material effects.

How it works

Conversions are computed by the unitfyi open-source engine (FYIPedia unitfyi-js, MIT): linear unit pairs convert through per-unit factors against a base unit, and temperature uses proper function-based formulas (°F = (°C × 9/5) + 32, K = °C + 273.15, and equivalents). Results are smart-rounded by the engine for readability. Unit names are matched against the engine's own alias tables, so km, kilometre, and kilometres all resolve to the same unit. Limitation: an unrecognized unit name returns an error listing the valid units for that category rather than guessing.

Examples

Kilometers to miles

Status: ok — 100 km = 62.1371 mi.

Celsius to Fahrenheit

Status: ok — 37 °C = 98.6 °F (body temperature).

Pounds to kilograms

Status: ok — converts imperial weight to metric.

People also search for these — this tool handles them all:

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