Onion converter: whole onions, cups, grams

A recipe says “1 cup chopped onion” or “2 medium onions” but you have a bag of large ones. Convert between whole onions and chopped cups, grams, or ounces so you chop exactly the right amount.

Onion size swings from a 70 g small to a 150 g large, more than double. Setting the size below means “1 cup chopped” comes out right whether your onions are small or jumbo.

How much does an onion weigh?

A medium, or average, onion weighs about 110 g, with a small one around 70 g and a large one around 150 g.

Related Onion Ingredients

Already chopping? The chopped onion converter moves straight between cups, grams, and spoons of prepped onion. See our Chopped Onion converter.

Need a milder, more delicate allium? Shallots (20–60 g) suit dressings and pan sauces. See our Shallot converter.

Spring onions (10–25 g) are tender and herbaceous, great raw or as a garnish. See our Spring Onion converter.

Mincing garlic for the same dish? Garlic cloves (2–7 g) bring pungent bite where onion brings sweet body. See our Garlic converter.

Want a crisp, peppery bite? Radishes (8–25 g) are sharp and crunchy, good raw in slaws or quick pickles. See our Radish converter.

Out of onion? See onion substitutes →

Onion converter tool

Enter an amount, pick your units, and set the size for counting whole onions.

Size applies to whole onions (small / medium / large).

Result

0.66 cups

Onion Calculators & Kitchen Tools

Working with onion? These tools handle the jobs a converter cannot.

  • Oven to Air Fryer Converter Match the temperature and time when you swap the oven for an air fryer, fan oven, or slow cooker.
  • Recipe Scaler Scale any recipe up or down and keep every ingredient in ratio.
  • Volume Converter Switch between cups, tablespoons, teaspoons and millilitres for any ingredient.
  • Weight Converter Switch between grams, ounces, pounds and kilograms for any ingredient.

Common Onion conversions

Quick reference for onion at medium size. Switch the size in the converter above for small or large.

onionsCups (chopped)
1 onion0.66 cups
2 onions1.32 cups
3 onions1.98 cups
4 onions2.63 cups
5 onions3.29 cups
6 onions3.95 cups

Onion conversion chart

The chart below shows how whole onions (medium size) convert to cups, grams and ounces.

onionscupscups (US)gozlbkg
1 onion0.66 cups0.69 cups (US)110 g3.88 oz0.24 lb0.11 kg
2 onions1.32 cups1.38 cups (US)220 g7.76 oz0.49 lb0.22 kg
3 onions1.98 cups2.06 cups (US)330 g11.64 oz0.73 lb0.33 kg
4 onions2.63 cups2.75 cups (US)440 g15.52 oz0.97 lb0.44 kg
5 onions3.29 cups3.44 cups (US)550 g19.4 oz1.21 lb0.55 kg

Onion varieties and best uses

The conversions above are the same whatever variety you use; the difference is what each is good for. Here is how the common onion varieties compare.

VarietyBest for
Yellow / brownAll-purpose cooking, soups, caramelising: balanced and sweetens when cooked.
RedRaw in salads and pickling: mild, colourful; also good roasted.
WhiteMexican dishes and salsa: sharp and clean raw.
Sweet (Vidalia / Walla Walla)Onion rings and raw slices: low pungency, high sugar.
ShallotDressings and pan sauces: delicate, subtle flavour.

Which should I pick?

For everyday cooking, soups, and caramelising, a yellow / brown onion is the default, with the most balanced flavour. For raw use in salads, salsa, or pickling, a red or sweet (Vidalia / Walla Walla) onion is milder. White onions suit Mexican dishes; shallots are the delicate choice for dressings and pan sauces.

Frequently Asked Questions

What is the size of a medium onion?
A medium onion weighs about 110 g, which works out to roughly 0.66 cups (0.69 US cups) of chopped flesh. Onions come in a range of sizes depending on the season, variety and where they were grown, so weight and cup figures shift accordingly. Use the size selector above to match what you actually have, then read the exact conversion for any amount.
How much does a medium onion weigh?
A medium onion weighs about 110 g, with a small one around 70 g and a large one near 150 g. That range changes the weight of any recipe that counts onions by the piece, so set the size selector to match what you actually have before trusting a cup or gram figure.
How much does an average onion weigh?
An average onion is the same as a medium one: about 110 g. A small onion is lighter at around 70 g and a large one heavier at about 150 g, so the size you actually have changes the total for any recipe that counts onions by the piece rather than by weight.
How much does a large onion weigh?
A large onion weighs about 150 g, noticeably more than a medium, or average, one at 110 g or a small one at 70 g. Set the size selector to large to convert cups, grams and ounces for the bigger onions you actually have on the counter.
Which onion variety should I use?
For everyday cooking, soups, and caramelising, a yellow / brown onion is the default, with the most balanced flavour. For raw use in salads, salsa, or pickling, a red or sweet (Vidalia / Walla Walla) onion is milder. White onions suit Mexican dishes; shallots are the delicate choice for dressings and pan sauces.
How do I convert grams to ounces for any ingredient?
Converting grams to ounces is pure weight maths that applies to any food, not just onions, so 200 grams is always 7.05 ounces. For other amounts, the weight converter at the link below handles grams, ounces, pounds, kilograms and stone in both directions. Grams to ounces converter

Onion measurement options

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