Unit Converter

Converting between units

This converter handles the three measurements people look up most: length, weight, and temperature. Pick a category, choose what you’re converting from and to, type a value, and the result appears instantly. Everything runs in your browser, so it’s fast and works offline once the page has loaded.

How the conversions work

Length and weight conversions are based on a fixed ratio to a base unit. For length, everything is defined relative to the meter — a mile is exactly 1,609.344 meters, a foot is 0.3048 meters — so converting is just multiplying and dividing by those factors. Weight works the same way relative to the kilogram. Because these factors are exact definitions, the results are precise rather than approximate.

Temperature is different: you can’t convert it by simple multiplication, because the scales don’t share a zero point. Instead we convert through Celsius using the standard formulas:

• °C to °F: °C × 9/5 + 32
• °F to °C: (°F − 32) × 5/9
• °C to Kelvin: °C + 273.15

Handy reference points

• 1 inch = 2.54 cm · 1 foot = 30.48 cm · 1 mile ≈ 1.609 km
• 1 kg ≈ 2.205 lb · 1 ounce ≈ 28.35 g · 1 stone = 14 lb
• 0 °C = 32 °F (water freezes) · 100 °C = 212 °F (water boils) · 37 °C ≈ 98.6 °F (body temp)

FAQ

Why does my result have lots of decimals?

Conversions between metric and imperial rarely land on round numbers, so we keep extra precision and let you round as needed.

Can I convert in either direction?

Yes — just swap the “from” and “to” units. The math is symmetric, so 5 km to miles and the reverse both work.

Which units does it support?

It covers the three categories people look up most: length (mm up to miles), weight (grams up to stone and pounds), and temperature (Celsius, Fahrenheit, and Kelvin). Pick a category first, then choose the from and to units within it.

Why can't I convert temperature by just multiplying?

Because temperature scales don't share a zero point — 0 °C isn't 0 °F — so a single ratio won't work. The converter applies the proper offset-and-scale formulas instead, such as °C × 9/5 + 32 for Fahrenheit, which is why those conversions are exact.

Is it free, private, and usable offline?

Yes — it's free with no sign-up, runs entirely in your browser so nothing is sent to a server, and works offline once the page has loaded. It's also fully usable on mobile.