1. Check the can size and tuna type

Start by reading the front and the nutrition label. A typical single-serve can is often around 5 ounces, while larger cans can be 7 ounces or more. Tuna packed in water and tuna packed in oil can have slightly different calories and fat, but the protein is usually similar per ounce.

As a practical rule, a standard 5-ounce can of tuna often provides roughly 20 to 30 grams of protein after draining, depending on the exact product and brand. Smaller cans may have closer to 15 to 20 grams; larger cans can be higher.

2. Use the label to calculate protein per can

Find three numbers on the label: protein per serving, servings per container, and serving size in ounces or grams. Then multiply protein per serving by servings per container. That gives you the protein in the whole can.

Example: if the label says 17 grams of protein per serving and 2 servings per can, the can contains about 34 grams of protein total. If the can has 1.5 servings at 13 grams each, the total is about 19.5 grams.

3. Count what you actually eat

If you eat the full can, use the full-can total. If you only eat part of it, estimate the fraction. Half a standard can with 24 grams of protein would give you about 12 grams.

If you drain the liquid, use the drained serving information when available. Some labels list serving size as drained tuna, which is the most useful number for tracking. If the label does not specify, compare the ounces of tuna sold with the drained weight listed on the package when possible.

4. Avoid the common mistakes

Do not assume every can has the same protein. Tuna packed in a larger can, a different cut, or a different brand may vary more than you expect.

Do not confuse calories with protein. Oil-packed tuna can be higher in calories, but the protein amount may stay fairly close to water-packed tuna. Also, do not guess based only on can size unless you have no label information.

If you eat tuna often, pay attention to mercury guidance and vary your protein sources. The CDC and other public-health sources advise being mindful about fish choices, especially for pregnant people and young children.

Tips

• Use the nutrition label first; it is more reliable than a generic estimate.
• Multiply protein per serving by servings per can to get the total quickly.
• Track drained tuna rather than the liquid if the label allows it.
• For meal prep, portion tuna into containers so your protein count stays consistent.
• If you’re using tuna around workouts, pair it with a carb source and hydration for a more balanced meal.