You’re standing in the kitchen, probably covered in a light dusting of flour or staring down a stubborn can of coconut milk, wondering exactly how much 13.5 ounces is in cups. It happens to the best of us. Most standard cans of coconut milk or specialty sauces come in that weird 13.5-ounce size, and it’s just enough to be annoying. It’s not a full two cups. It’s definitely more than one.
So, what’s the damage? 13.5 ounces is exactly 1.6875 cups.
Nobody has a 0.6875 measuring cup. That’s just not how life works. If you’re looking for a quick, "close enough for government work" answer, it’s basically 1 ¾ cups minus two teaspoons. If you’re baking a delicate souffle, that tiny difference might matter. If you’re making a Thai green curry? It really doesn’t. Just dump the can in and move on with your life.
Why 13.5 Ounces is How Many Cups Matters for Your Cooking
Most people assume that because a cup is 8 ounces, two cups must be 16 ounces. That’s solid logic. But then you hit the 13.5-ounce hurdle. This specific measurement is a staple in international canning standards, particularly for liquids like coconut milk or evaporated milk. If you’re following a recipe that calls for two full cups of liquid and you only have one 13.5-ounce can, your dish is going to be dry. You’re missing about 2.5 ounces, which is roughly five tablespoons.
That’s a lot.
Think about the physics of a cake or a sauce. Liquid isn't just for flavor; it’s for hydration and heat distribution. When you short-change a recipe by nearly a third of a cup, you’re changing the viscosity. The "13.5 ounces is how many cups" question isn't just about math—it's about whether your dinner turns out like a silky sauce or a thick, gummy paste.
The Dry vs. Liquid Ounce Trap
Here’s where things get messy. Are we talking about fluid ounces or weight ounces? In the US, we use the same word for two different things, which is honestly a terrible system.
Fluid ounces measure volume. Weight ounces measure mass.
If you have 13.5 ounces of water, it’s 1.68 cups. If you have 13.5 ounces of lead buckshot, it’s definitely not going to fit in a cup and a half. Even in the kitchen, 13.5 ounces of flour weighs much more in volume than 13.5 ounces of water because flour is fluffy and less dense. For most people asking about 13.5 ounces, they are looking at a liquid measuring cup or a tin can. In that context, we are sticking to fluid ounces.
Breaking Down the Math (The Boring but Necessary Part)
If you really want to get technical—and since you’re reading this, you probably do—here is how the math breaks down for 13.5 ounces:
One US Standard Cup = 8 Fluid Ounces.
To find the cup count, you divide 13.5 by 8.
$13.5 / 8 = 1.6875$
To visualize this in your kitchen:
- 1 cup (8 oz)
- 1/2 cup (4 oz)
- 2 tablespoons (1 oz)
- 1 tablespoon (0.5 oz)
So, 13.5 ounces is one cup, plus a half cup, plus exactly three tablespoons.
Actually, wait. Let's re-verify that. 8 + 4 = 12. Then you need 1.5 more ounces to hit 13.5. Since one ounce is two tablespoons, 1.5 ounces is exactly three tablespoons.
1 Cup + 1/2 Cup + 3 Tablespoons = 13.5 ounces.
There. That’s much easier to measure than 0.6875 of a cup.
What About the Rest of the World?
If you’re reading a recipe from the UK, Australia, or Canada, they might be using "Metric Cups." A metric cup is 250 milliliters. A US cup is roughly 236.5 milliliters. This doesn't seem like a big deal until you're scaling up a recipe for a party of twenty.
In the metric world, 13.5 US fluid ounces is approximately 400 milliliters.
Most standard "400ml" cans sold globally are actually about 13.52 ounces. Manufacturers just round it down for the US label to keep things "clean." If you use a metric cup (250ml), your 13.5 ounces is only about 1.6 cups.
It’s a headache. Stick to your local measuring spoons if you can.
Practical Examples: Coconut Milk and Beyond
The most common place you'll see this number is on a can of Thai Kitchen or Chaokoh coconut milk. They almost all come in 13.5 fl oz (400 ml) containers.
I once tried to make a vegan panna cotta that called for exactly 2 cups of coconut milk. I thought, "Hey, one can is probably enough." It wasn't. The panna cotta didn't set right because the ratio of agar-agar to liquid was skewed. I was short by that 2.5 ounces we talked about earlier.
If your recipe specifically calls for "two cups," and you only have one 13.5-ounce can, you have two choices:
- Scale the recipe down. Multiply all your other ingredients by 0.84. (Good luck doing that with half an egg).
- Top it off. Add a little water, broth, or dairy milk to the coconut milk until it hits the 16-ounce (2 cup) mark.
In most savory cooking, topping it off with a bit of water won't hurt. In baking, you might want to be more careful.
Is 13.5 Ounces a "Standard" Size?
Not really. Not in the US, anyway. Our standard small cans (like tomato sauce) are usually 8 ounces or 15 ounces. The 13.5-ounce size is an interloper. It’s the result of the global supply chain. Since 400ml is a standard round number in the metric world, and that converts to 13.5256 ounces, US importers just slap "13.5 oz" on the label and call it a day.
It’s literally a metric measurement wearing a US Customary suit.
Why Precision is a Myth in the Kitchen
Look, unless you are working in a laboratory or a high-end patisserie, "13.5 ounces is how many cups" is a question with a bit of wiggle room.
Humidity affects how flour packs into a cup. The temperature of your oil changes its volume slightly. Even the way you pour—whether you create a meniscus (that little curve at the top of the liquid) or not—can change your measurement by a teaspoon or two.
If you are stressed about that extra 0.1875 of a cup, just remember that Grandma probably used a "teacup" and a "handful" and her biscuits were still better than yours.
Helpful Conversion Shortcuts for 13.5 Ounces
If you don't want to do the math every time, just keep these approximations in your head:
- It’s roughly 1 and 2/3 cups.
- It’s slightly less than 1 and 3/4 cups.
- It’s about 400 milliliters.
- It’s 27 tablespoons. (Don't actually measure it by the tablespoon. You'll go insane.)
Measuring 13.5 Ounces Correctly
If you want to be perfect, stop using cups. Use a scale.
Professional chefs like J. Kenji López-Alt or Stella Parks constantly advocate for weight-based cooking. Why? Because 13.5 ounces on a digital scale is always 13.5 ounces. It doesn't matter if the liquid is bubbly, thick, cold, or hot.
If you use a glass measuring cup, get down at eye level. If you look at the line from above, you’ll likely over-pour. This is called a parallax error. It’s the same reason your speedometer looks like it’s pointing at 65 when your passenger thinks you’re doing 60.
When 13.5 Ounces is Not 13.5 Ounces
Wait, what?
Yeah. If you're measuring something like honey or molasses, the "13.5 ounces" on the label is likely weight, not volume. Because honey is so dense, a 13.5-ounce jar of honey is actually much less than 1.68 cups. It’s closer to 1.1 cups.
Always check the label. If it says "NET WT," it’s weight. If it says "FL OZ," it’s volume. This is the single biggest mistake people make when trying to figure out 13.5 ounces is how many cups.
How to Proceed with Your Recipe
If you’re currently staring at a 13.5-ounce can and a recipe that wants "cups," take a breath.
For soups, stews, and curries, treat the can as 1.7 cups and don't worry about the tiny deficit. If the sauce looks too thick, add a splash of water.
For bread, cakes, or cookies, you need to be precise. Measure out your 1 cup, then your 1/2 cup, and then add 3 level tablespoons. That will give you the 13.5 ounces the recipe is likely looking for if it was developed in a metric-standard country.
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If you find yourself doing this conversion often, buy a measuring cup that has milliliters on one side and ounces on the other. It saves so much mental energy. You can just pour to the 400ml mark and know you're exactly at that 13.5-ounce sweet spot.
Stop overthinking the decimals. Cooking is supposed to be fun, not a calculus final. Use the "cup and a half plus three tablespoons" rule and get back to the stove.
Actionable Next Steps:
- Check your can label to see if it lists "FL OZ" or "NET WT" before converting.
- Use a liquid measuring cup at eye level for the 1.7-cup approximation.
- If baking, use a kitchen scale and set it to grams (400g for most liquids) for better accuracy.