When you start out cooking, measuring everything exactly can be a big concern, which is why beginning cooks may be put off by recipes that list vague amounts such as "a pinch of salt" or "one medium onion". Though "pinch" has been pretty much standardised -- it's agreed upon to be an 1/8th of a teaspoon -- a "medium" onion is a little harder to pin down.
Photo by Xiaojun Deng.
The good news is this: It's OK if you're a little imprecise with your onion. Unlike ingredients used in baking, no culinary chemical reactions are hinging on how much onion you're using. It is, however, nice to have guidelines, especially when you're just starting out, so here are some approximations to make sure you're not adding too much or too little onion in your dish:
- Small: A small onion should weigh around 113g, should fit pretty easily in your hand, and should yield about 1/2 cup once chopped.
- Medium: A medium onion is about twice as big as a small one, weighing it at roughly 226g and yielding (you guessed it) about a cup once chopped.
- Large: Large onions are three times larger than small onions (340g), and should give you about 1 1/2 cups of chopped onion once you get at it with a knife.
Obviously, it's unlikely that you're going to find onions that are exactly 4, 8 or 340.19g, but things like this are why I always recommend that everyone own a kitchen scale. But if you don't yet have a scale, I wouldn't worry too much; an extra few grams of onion isn't going to ruin your soup or meatloaf or whatever. Extra onion never ruined anything.
This is part of The Grown Up Kitchen, Lifehacker's series designed to answer your most basic culinary questions and fill in any gaps that may be missing in your home chef education.