Onion Measurements – The Ultimate Guide

Common onion measurements to help you determine how many onions you need per recipe. Some recipes call for one large onion, others call for 1 cup diced onions and some may say one small onion. It can be confusing to know just how many onions to buy or to chop. Here’s the general rule of thumb and some detailed info on common onion measurements.

General Rule of Thumb: 1 medium onion = 1 cup of diced onions

This is the standard you’ll find in most recipes.

PRO TIP: The way onions are used in most recipes means there is a lot of leeway in how many onions to add. Usually, it’s okay to use whatever you have – small, medium or large onions. Often, it’s even okay to add that extra half onion in your fridge. This is true for recipes like soups, stews, casseroles, curries, chili, frittatas, etc.

Onion weights

  • Large onion is 225-275 g or 8-9 oz
  • Medium onion is 150-170g or 6 oz
  • Small onion is 125 g or 4 oz

The Ultimate Guide to Onion Measurements

Need a more details? Check out this handy dandy infographic I made.  I call it The Ultimate Guide to Onion Measurements.  There’s an imperial and metric version.

Onion Measurement Imperial

For those who prefer metric measurements.

Ultimate Guide to Onion Measurements Metric

Have an onion question that’s not covered? I’m happy to help – just let me know via the comments below or share a photo on Instagram and tag #getgettys.

Sign up to get articles by Getty delivered to your inbox. You’ll get recipes, practical tips and great food information like this. Getty is a Professional Home Economist,  speaker and writer putting good food on tables and agendas.  She is the author of Manitoba’s best-selling Prairie Fruit Cookbook, Founder of Fruit Share, a mom and veggie gardener.

Similar Posts


    1. Hmm, good question, you’re best off to ask wherever you found that measurement listed.
      Could it mean 1 onion is 1 unit? That would be my guess, but depends on the recipe.
      Often the exact measurement of onion is pretty forgiving. Look at other similar recipes and see what they’re standard is.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.