A recipe rarely arrives in the measurements your own kitchen uses. A video from an American food blogger lists cups and ounces. An old family recipe card gives pints and ounces. A recipe shared by a friend in Australia uses a tablespoon that's a different size to the one in your drawer. None of that is a problem until you're standing at the hob trying to work out what 350°F means on your oven dial, or how many grams are hiding inside a cup of flour.
The Recipe Unit Converter takes a quantity in one system and gives you the equivalent in another, so you can follow a recipe in the units your scales, jugs and spoons actually understand.
Why the same recipe uses different units
Weight, volume and temperature each have more than one system in everyday use, and a recipe tends to carry whichever one its writer grew up with. Grams and millilitres are standard in British kitchens. Cups, tablespoons and Fahrenheit are standard in American ones. Older British recipes mix in pints, pounds and ounces from before metric became the norm here. None of these is wrong, they're just different starting points, and a recipe written for one doesn't automatically translate to another.
What the converter works out for you
You enter a quantity and tell it what it's measuring and in what unit, and it gives you the equivalent in the unit you want to cook with. That covers weight (grams, ounces, pounds), volume (millilitres, cups, tablespoons, teaspoons, pints) and oven temperature (Celsius, Fahrenheit, gas mark). You can go in either direction, so a recipe you've written yourself in grams can be converted the other way for someone cooking from cups.
Where a conversion can mislead you
A cup of flour and a cup of golden syrup don't weigh the same, because volume and weight only line up once you know how dense the ingredient is. The converter works from standard figures for common ingredients, and those are averages. How tightly flour is packed into a cup, whether a tablespoon is levelled or heaped, and the exact variety of an ingredient can all shift the true weight a little either way. For most weeknight cooking that difference won't matter. For baking, where the ratio of flour to liquid to raising agent is doing real work, it can be the difference between a cake that rises and one that doesn't, so it's worth weighing on scales where the recipe allows it.
Oven temperature conversions carry their own catch. Gas marks, Celsius and Fahrenheit don't map onto each other in perfectly even steps, and ovens themselves run hotter or cooler than their dial suggests. Treat a converted oven temperature as a starting point and check the food.
Using it alongside the rest of your cooking
Converting units often comes up at the same time as converting portions, say when a recipe written to feed six needs to stretch to feed four. The Recipe Portion Scaler handles that side of it, and the two work well run one after the other on the same recipe. If you want more on how that scaling works, the guide to the Recipe Portion Scaler walks through it.
For the full set of tools built for everyday cooking decisions, the guides index lists what else is there.