You’re standing in the grocery aisle, looking at a stack of StarKist or Bumble Bee. You remember these things being bigger. You aren't crazy. For decades, the standard weight was a solid six ounces, but if you flip that tin over today, you’re likely looking at five. Or maybe even less.
It’s called "shrinkflation," and it’s basically the silent killer of your tuna salad recipe.
Understanding how many ounces in a tuna can really comes down to whether you’re talking about the weight of the metal tin, the "net weight" printed on the label, or the actual amount of fish you get to eat after you’ve squeezed all that salty water down the drain. It’s a bit of a shell game. Brands have mastered the art of making the packaging look identical while slowly shaving off fractions of an ounce to keep prices stable while their costs go up.
The 5-Ounce Standard and Why It Changed
Most tuna cans you buy at a place like Kroger or Walmart today are 5 ounces (142 grams). That is the industry standard for a "regular" size. But it’s a relatively recent shift. Back in the day—we're talking the 1980s and 90s—the 6-ounce can was king. Around 2008, the major players like Chicken of the Sea and StarKist made a coordinated move toward the 5-ounce can. They kept the diameter of the can the same so it would still fit in your hand and stack on shelves properly, but they made the walls slightly shorter. You probably didn't even notice unless you were really looking at the fine print.
Why? Money.
It costs a lot to catch, process, and ship tuna. When fuel prices spike or tuna populations fluctuate, companies have two choices: raise the price or give you less fish. They almost always choose the latter because shoppers are more sensitive to a $1.50 can becoming $1.75 than they are to a 6-ounce can becoming a 5-ounce can.
But wait, it gets even weirder. Some "premium" brands or specialty cuts, like solid white albacore, might still flirt with different sizes. You’ll occasionally find 4.5-ounce cans hiding in the mix, especially in those fancy "no-drain" varieties.
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Drained Weight vs. Net Weight: The Big Lie
Here is the thing that really bugs people. You see "5 oz" on the front, but when you dump that can out into a bowl, it looks... pathetic. That’s because the 5-ounce measurement is the Net Weight. That includes the liquid.
According to the FDA and standard industry practices, that liquid (whether it’s spring water, vegetable oil, or brine) counts toward the total weight. If you’re a stickler for the math, you should look for the "Drained Weight." This is the actual amount of protein you're consuming.
What are you actually getting?
- In a standard 5-ounce can of chunk light tuna in water, you’re actually getting about 3 to 3.5 ounces of actual fish.
- In an oil-packed can, the tuna often retains a bit more weight because the oil doesn't leech out the moisture from the fish as aggressively as water does, but it’s still significantly less than five ounces.
- If you buy the 2.5-ounce pouches, what you see is basically what you get. Those are "no-drain," so the 2.5 ounces listed is almost entirely meat.
If you’re trying to hit a specific protein goal for a workout plan, don't track 5 ounces of tuna. You're tracking about 3.25 ounces of solids. Honestly, if you’re using an old family recipe that calls for "two cans of tuna," your grandma was probably using 12 ounces total. Using two modern cans only gives you 10 ounces. Your tuna melt is going to be thin. You might need a third can just to keep the proportions right.
Comparing the Giant Tins and the Tiny Tins
Not everyone buys the single-serve hockey puck. If you’re at Costco or prepping for a massive party, you’ve seen the "Big Kahuna" of tuna cans.
- The 7-Ounce Can: This is becoming rarer, but some luxury brands like Tonnino or Ortiz sell glass jars or slightly larger tins in the 6.7 to 7-ounce range. These are usually solid fillets, not "chunks."
- The 12-Ounce Can: Often found in the "family size" section. It’s exactly what it sounds like. It’s meant for families of four or people who really, really like tuna.
- The 66.5-Ounce Can: This is the food-service monster. You’ll see these at Subway or in school cafeterias. It’s over four pounds of tuna. If you buy one of these at a warehouse club, make sure you have a plan to eat it quickly once it's open, because that is a lot of fish to get through before it starts smelling funky in your fridge.
Does the Can Size Affect the Quality?
Kinda.
There’s a weird physics thing that happens during the canning process. Tuna is cooked inside the can. This is called "retort" processing. The heat penetrates the can from the outside in. In a smaller 5-ounce can, the heat reaches the center relatively quickly. In a massive 66-ounce catering tin, the fish near the edges has to sit under high heat for much longer to ensure the middle is safely cooked.
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This is why "Solid White Albacore" in a small can often tastes firmer and fresher than the stuff that comes out of a giant vat. The smaller the container, the less "overcooked" the fish tends to be. That’s also why those 2.5-ounce foil pouches often taste better than cans—they’re thinner, so they require less heat-time to sterilize.
Is More Ounces Always Better?
You’d think so. But you’ve got to watch out for the mercury.
The bigger the can, the more tempting it is to eat the whole thing. But the FDA and the EPA have pretty specific guidelines on this. Albacore (White) tuna is a larger fish and lives longer, meaning it accumulates more mercury. They suggest kids and pregnant women limit it to about 4 ounces a week.
If you’re eating a modern 5-ounce can of Albacore, you’ve already exceeded that recommendation in one sitting. Chunk Light tuna, which usually comes from smaller Skipjack tuna, is much lower in mercury. You can usually get away with two or three 5-ounce cans a week of the light stuff.
The Math of Your Grocery Bill
Let’s talk value.
Price per ounce is the only way to shop for tuna. If you see a 5-ounce can for $1.50, you’re paying 30 cents an ounce. But wait—that’s 30 cents per wet ounce. If the drained weight is only 3.5 ounces, you’re actually paying about 43 cents per ounce of actual food.
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Compare that to the 2.5-ounce pouches. If a pouch is $2.00, you’re paying 80 cents per ounce. You’re paying a massive premium for the convenience of not having to use a can opener or drain the stinky water into your sink. Is it worth it? For a hiking trip, maybe. For a Tuesday lunch at home? Probably not.
How to Get the Most Out of Your Ounces
If you’re tired of opening a can and seeing more water than fish, there are a few things you can do.
First, look for "Solid" instead of "Chunk." Solid tuna is literally a steak cut to fit the can. There’s less surface area for water to soak into, and you generally get a higher weight of actual meat. Chunk tuna is the leftovers—the bits and pieces. It’s cheaper, but it’s also much mushier and holds more liquid.
Second, consider the oil-packed options. While people avoid them for "health" reasons (the calories are higher), oil-packed tuna is significantly more satiating. You’re getting more "food" and less "filler." Plus, you can use the oil from the can to sauté aromatics for a pasta dish, which means you aren't wasting any of those ounces you paid for.
Third, check the bottom of the can for a "Drained Weight" stamp. Not all brands do it, but some honest ones will tell you exactly what’s left after the water is gone. If they don't, you can do a rough estimate: expect to lose about 30% of the labeled weight to liquid.
Actionable Steps for the Smart Shopper
- Check the label every time. Don't assume the brand you’ve bought for ten years is still 5 ounces. Companies are testing 4-ounce and 4.5-ounce sizes in certain markets right now.
- Calculate the "True Cost." Divide the price by the net weight, then add about 30% to that price to figure out what you're actually paying for the meat.
- Stock up when the 12-ounce cans go on sale. The price per ounce is almost always better on the larger tins, and they have a shelf life of three to five years.
- Switch to Light Tuna for volume. If you want to eat a bigger tuna salad without the mercury risk, skip the Albacore and stick to the 5-ounce Chunk Light tins.
- Save the liquid (sometimes). If you’re buying tuna in water, your cat will love that 1.5 ounces of "tuna juice." If you bought it in oil, that’s basically flavored cooking oil—don't just pour it down the drain.
The reality of the grocery store is that things are getting smaller while prices are staying the same. The 5-ounce tuna can is the poster child for this trend. By knowing exactly how much fish is actually in that tin, you can stop overpaying for salt water and start making better decisions at the checkout counter.