Quick answer
Generally, 1 small onion yields about 1/2 to 3/4 cup of chopped onion. So if you need 1 small onion chopped, plan on using between 1/2 and 3/4 cup of pre-chopped onion. The exact amount can vary based on the size of the onion and how finely it is chopped.
What size is a small onion?
Onions come in different sizes, so a “small” onion can have some variability. In general, a small onion is approximately 2-3 inches (5-7.5 cm) in diameter. Its weight can range from around 2-4 ounces (57-113 grams).
Some standard onion size classifications are:
| Onion Size | Diameter | Weight |
| Small | 2-3 inches | 2-4 oz |
| Medium | 3-4 inches | 5-8 oz |
| Large | Over 4 inches | Over 8 oz |
So when a recipe calls for 1 small onion, you can expect it to be in the range of 2-3 inches wide and weigh about 2-4 ounces. This will help you estimate how much chopped onion you need.
How finely chopped is chopped onion?
The fineness of the chop also affects how much volume you get from an onion. Finely diced onion will pack down into a smaller space than coarsely chopped onion pieces.
Some standard onion chop sizes are:
| Chop Type | Approximate Size |
| Diced/finely chopped | 1/8-1/4 inch |
| Chopped | 1/4-1/2 inch |
| Coarsely chopped | 1/2-1 inch |
When a recipe simply calls for a “chopped” onion, it often means a medium chop with pieces between 1/4-1/2 inch. Finely diced onion will take up around 1/2 cup per small onion, while coarsely chopped will be closer to 3/4 cup.
How to substitute chopped onion for whole onion
When substituting chopped onion for whole onion called for in a recipe, first look at the size descriptor (small, medium, large) and use that to estimate how much onion you need. Then account for how finely it is chopped.
Here are some general substitution guidelines:
| Whole Onion Called for | Use This Much Chopped Onion |
| 1 small onion, diced | 1/2 cup chopped |
| 1 small onion, chopped | 1/2 to 2/3 cup chopped |
| 1 small onion, coarsely chopped | 2/3 to 3/4 cup chopped |
| 1 medium onion, diced | 3/4 cup chopped |
| 1 medium onion, chopped | 3/4 to 1 cup chopped |
| 1 large onion, diced | 1 to 1 1/4 cups chopped |
| 1 large onion, chopped | 1 1/4 to 1 1/2 cups chopped |
Keep in mind that these are approximate ranges. The exact amount can vary based on the actual size of the onion and your personal chopping style. When in doubt, start with less chopped onion and add more as needed.
Tips for chopping onions
Here are some tips for efficiently and uniformly chopping onions:
- Trim off the root and stem ends of the onion first.
- Peel off the papery outer skin.
- Cut the onion in half from root to stem end.
- Place each half flat side down on a cutting board.
- Make horizontal slices from one end to the other, leaving the root end intact.
- Make vertical slices across the horizontal cuts to dice the onion.
- For a finer dice, chop the diced pieces a few more times.
- Use a sharp knife and be careful not to cut yourself.
- Chill onions for 30 minutes before chopping to prevent teary eyes.
Practice chopping onions to get a feel for how much yield you get from different sizes and chop styles. This will help you become better at estimating chopped onion amounts.
Storing chopped onions
Chopped onions start to lose their flavor and moisture quickly. For best quality and flavor, it’s best to chop onions right before cooking.
However, you can store chopped onions in the refrigerator for 2-3 days if needed:
- Place chopped onions in an airtight container.
- Spread the onions out in a single layer, not piled up.
- Cover and refrigerate for up to 3 days.
Onions can also be frozen for longer storage:
- Chop onions as needed.
- Spread chopped onions out on a plate or baking sheet.
- Place in freezer for 1-2 hours until completely frozen.
- Transfer to airtight bags or containers.
- Remove as much air as possible.
- Label with date and freeze for up to 3 months.
Frozen onions may lose some crispness but can be used in cooked dishes. Thaw in the refrigerator before using.
Common uses for chopped onions
Chopped onions are a versatile ingredient and aromatically infuse many savory dishes. Here are some of the most common ways to use them:
- Sautéing – Cook chopped onions in oil or butter over medium heat until tender and translucent.
- Soup bases – Sautéed onions provide flavor and texture to soups and broths.
- Casseroles – Mix chopped onions into egg and rice dishes like stratas or omelets.
- Salads and salsas – Raw chopped onions add bite to fresh salsa and salad recipes.
- Sandwiches and tacos – Caramelized onions, raw onions, and onion relish top burgers, sandwiches, and tacos.
- Pizza – Sprinkle crispy chopped onions over pizza before baking.
- Pickling – Quick-pickled red onions brighten up grain bowls, salads, and charcuterie boards.
Onions are so useful in cooking because they add tons of flavor for few calories. Keep your fridge stocked with chopped onions so they’re ready to cook into your favorite dishes.
Onion equivalents and conversions
When shopping, cooking, or following a recipe, you may need to make substitutions or conversions between different forms of onions, such as:
- Whole onions to chopped onions
- Yellow, white, or red onions
- Reconstituted dried onion flakes or powder
- Dehydrated onions
Here are some handy onion conversion equivalents to help:
| 1 small onion, chopped (1/2 cup) | = 1/4 cup dried onion flakes, reconstituted |
| = 1 tablespoon onion powder + 1 tablespoon water | |
| = 1/3 cup dehydrated chopped onions, reconstituted | |
| = 2 tablespoons freeze-dried onions reconstituted | |
| = 1 small Vidalia, yellow, or white onion | |
| 1 medium onion, chopped (1 cup) | = 1/2 cup dried onion flakes, reconstituted |
| = 2 tablespoons onion powder + 2 tablespoons water | |
| = 2/3 cup dehydrated chopped onions, reconstituted | |
| = 1/4 cup freeze-dried onions reconstituted | |
| = 1 medium Vidalia, yellow, or white onion | |
| 1 large onion, chopped (1 1/2 cups) | = 3/4 cup dried onion flakes, reconstituted |
| = 3 tablespoons onion powder + 3 tablespoons water | |
| = 1 cup dehydrated chopped onions, reconstituted | |
| = 1/3 cup freeze-dried onions reconstituted | |
| = 1 large Vidalia, yellow, or white onion |
To reconstitute dried onion flakes or dehydrated onions, place in a bowl and add enough warm water to cover. Allow to sit for 5-10 minutes to rehydrate before draining and using.
Measure chopped onions by weight for precision
For the most accuracy, it’s best to measure chopped onions by weight instead of volume. Different chop sizes can drastically affect how much space onions take up in a measuring cup.
Here are some guidelines for weights:
- 1 small onion = around 2-4 ounces chopped
- 1 medium onion = around 5-8 ounces chopped
- 1 large onion = around 8-12 ounces chopped
Investing in a digital kitchen scale removes the guesswork and yields more reliable results in recipes. Weighing onions after chopping gives you an exact measurement for precision cooking.
Buy pre-chopped onions to save prep time
While freshly chopping an onion provides the best flavor and texture, you can also save time by purchasing pre-chopped onions. Look for them in the refrigerated produce section of the grocery store.
- Mild or strong, yellow, white, red, and sweet onions are often available pre-chopped.
- They are more expensive than whole onions per pound.
- Store-chopped onions are usually diced or minced.
- You can still estimate 1 small onion as 1/2 to 3/4 cup chopped.
- Use within a week for best quality and flavor.
Pre-chopped onions are handy when you need just a small amount. But chopping a batch of onions yourself can be more economical for large quantities.
Conclusion
So in summary, for 1 small onion you’ll need around 1/2 to 3/4 cup of chopped onion – keeping in mind the variability based on onion size, chop style, and density. Weighing chopped onions removes the guesswork for the most accuracy in recipes. And remember that nothing beats the flavor of freshly chopped onions – but pre-chopped can save time in a pinch.
