Unit Converter

Eight measurement domains in a single page, with the conversion factors stated so you can check them. Pick a domain, choose your two units, and type a value. The formula appears underneath, and a reference table shows common values for whichever pair you have selected.

How to use it

1. Choose a domain from the dropdown: length, weight, volume, temperature, speed, data, area or time.
2. Pick the unit you are converting from and the unit you want.
3. Type your value. The result updates as you type, and the exact relationship between the two units is shown below it.
4. Press the swap button to reverse the direction without re-selecting anything.
5. On volume or weight, choose an ingredient in the cooking panel to convert between cups and grams properly.

A cup of flour and a cup of honey are not the same

Here is the conversion nearly every unit converter gets wrong, and it matters most in the place people use it most: the kitchen.

Cups measure volume. Grams measure mass. Converting between them requires knowing the density of the substance, and ingredients differ enormously. A US cup of water weighs about 237 grams. The same cup filled with plain flour holds roughly 125 grams — barely half. Fill it with honey and you get about 340 grams. Cocoa powder is 86 grams. Table salt is 292.

So “1 cup = 240g” — which is what a converter tells you when it silently assumes water — is wrong by a factor of nearly three depending on what you are measuring. In a bread recipe, using 240 grams of flour where 125 was intended does not produce a slightly different loaf. It produces a brick.

This is why the cooking panel here asks which ingredient you are measuring, and why it lists fourteen of them with their actual mass per US cup. It is also part of why recipes written by weight are more reliable than recipes written by volume: a gram of flour is a gram of flour regardless of how firmly it was scooped, whereas a “cup” of flour varies by 20% or more depending on whether it was spooned in gently or packed down.

The same logic applies to the US and UK measures listed separately throughout. A US cup is 237ml, a UK metric cup is 250ml, a US pint is 473ml and a UK pint is 568ml. These are not rounding differences, they are different units that happen to share a name, and a recipe that calls for a pint means one or the other.

What it does not do

It converts between units, not between currencies — exchange rates change by the minute and would need a live data source, which this site does not use. It does not handle fuel economy directly, since MPG and litres per 100 km are inverse scales rather than a simple ratio; the fuel cost calculator handles that properly. Ingredient densities are typical values from standard references and will vary a little by brand, grind and humidity, so treat them as accurate to within a few per cent rather than exact.

Volume: US against UK

Unit	Millilitres	Notes
US teaspoon	4.93
US tablespoon	14.79
US fluid ounce	29.57
UK fluid ounce	28.41	Smaller than the US one
US cup	236.59
UK metric cup	250.00
US pint	473.18	16 US fl oz
UK pint	568.26	20 UK fl oz
US gallon	3785.41
UK gallon	4546.09	About 20% larger

Grams per US cup, by ingredient

Ingredient	Grams per cup
Flour, plain	125
Flour, bread	127
Sugar, granulated	200
Sugar, brown, packed	220
Sugar, icing	120
Butter	227
Oil, vegetable	218
Water	237
Milk, whole	244
Honey	340
Rice, uncooked	185
Oats, rolled	90
Cocoa powder	86
Salt, table	292