You're standing in the kitchen, probably covered in a bit of flour or halfway through prepping a smoothie, and you see it. The recipe calls for 300 ml. You look at your measuring cup. It’s got lines for cups and ounces, but the metric side is faded or just non-existent. You need to know how many ounces is 300 ml and you need to know right now before the pan gets too hot.
Here is the quick, no-nonsense answer: 300 ml is roughly 10.14 fluid ounces.
But honestly? If you just use 10 ounces, you’re usually fine. Except when you aren't. Precision matters in some places and is totally overkill in others. If you’re making a cocktail, that extra .14 might not break the drink. If you are diluting medication or working on a very temperamental pastry crust, that tiny sliver of a fraction actually starts to carry some weight.
Why the Math Gets Weird
Converting 300 ml to ounces isn't as straightforward as we’d like because the world can't agree on what an ounce actually is. It’s annoying. We have the Imperial system and the US Customary system.
In the United States, we use the US fluid ounce. To get the number, you divide your milliliters by 29.57. So, $300 / 29.57 = 10.1442$. Most people just round that down. However, if you are in the UK or using an old British cookbook, they use the Imperial fluid ounce. That one is slightly smaller. For an Imperial conversion, 300 ml is about 10.56 ounces.
That is a half-ounce difference!
Think about that for a second. A half-ounce is a tablespoon. If you use a British recipe but a US measuring cup, you might be adding an extra tablespoon of liquid you didn't intend to. It’s these little discrepancies that make your cake sink in the middle or make your "famous" soup taste a little too watery one day and perfect the next.
300 ml in the Real World
What does 300 ml actually look like? It’s a bit of an odd volume. It’s more than a standard cup but less than a pint.
Most standard coffee mugs in the US hold about 8 to 12 ounces. So, 300 ml is basically a full, standard mug of coffee. If you’re looking at a soda can, those are 12 ounces (355 ml). So, 300 ml is a soda can minus a few big gulps.
In the health world, 300 ml is a very common size for a small bottle of water or a protein shake. If you’re tracking your intake and your bottle says 300 ml, you’re hitting just over 10 ounces.
The Cooking Factor
When I’m cooking, I rarely grab the calculator. I use mental shortcuts.
- 100 ml is about 3.4 ounces.
- 200 ml is about 6.8 ounces.
- 300 ml is about 10.1 ounces.
If a recipe asks for 300 ml of chicken stock, I’m pouring a 10-ounce pour and calling it a day. It’s stock. It evaporates. It’s fine. But if I’m working with heavy cream for a ganache? I’m much more careful. Fats and liquids in baking rely on specific ratios to emulsify. If you have too much liquid, your chocolate won't set. You’ll end up with a sauce instead of a frosting.
Beyond the Measuring Cup: The Science of ml to oz
Scientists at the National Institute of Standards and Technology (NIST) spend their whole lives making sure these measurements are exact. They don't "eyeball" it. In a lab setting, 300 ml is exactly 300 cubic centimeters of water at a specific temperature.
Temperature actually changes volume.
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Water expands when it gets hot. If you measure 300 ml of boiling water, it’s actually slightly less "stuff" than 300 ml of ice-cold water. For the home cook, this is nerd-level trivia. For a chemist, it's the difference between a successful experiment and a disaster.
When you ask how many ounces is 300 ml, you are usually asking for the volume. But keep in mind that "ounces" can also mean weight (avoirdupois ounces). 300 ml of water weighs about 10.58 ounces in mass. But 300 ml of honey? That’s going to weigh way more because honey is denser.
Never use a kitchen scale set to "ounces" to measure 300 ml of a heavy liquid unless the scale has a specific "fluid ounce" setting that accounts for the density of water.
Common Misconceptions About 300 ml
People often think a cup is 250 ml. It's not. Not exactly.
A legal US cup is 240 ml. So, 300 ml is one cup plus 60 ml. 60 ml is exactly four tablespoons.
So, here is your easiest kitchen hack: If you need 300 ml, measure out one level cup and then add four tablespoons. No calculator required. No googling while your hands are covered in raw egg.
I've seen people try to use the "quarter-liter" rule too. They think 300 ml is just "roughly" a quarter of a liter. Nope. A quarter liter is 250 ml. You’re missing 50 ml—that’s nearly two full ounces. If you make that mistake in a recipe for bread, your dough is going to be incredibly dry and tough.
How to Get It Right Every Time
If you’re tired of doing the mental gymnastics of how many ounces is 300 ml, it might be time to change how you work.
- Buy a dual-scale pitcher. Seriously. Get a glass Pyrex that has milliliters on one side and ounces on the other. It eliminates the "math tax" on your brain.
- Go Metric. Most professional bakers and chefs prefer grams and milliliters. It’s base-10. It’s clean. It’s hard to mess up.
- Use a Scale. The most accurate way to measure 300 ml of water is to put a bowl on a digital scale, tare it to zero, and pour until it hits 300 grams. Because 1 ml of water equals 1 gram. It’s a beautiful, perfect 1:1 ratio.
Actionable Next Steps
To make sure your next meal or project is perfect, don't just guess. If you need exactly 300 ml and only have an ounce-based tool, fill your measuring cup to the 10-ounce mark, then add just a tiny splash (about three-quarters of a teaspoon) to account for that .14.
For those using a standard 8-ounce measuring cup, you'll need to fill it to the top, pour it into your mixing bowl, and then add another 2 ounces (which is 4 tablespoons). This gets you to 10 ounces, which is close enough for 99% of household tasks.
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Keep a small conversion chart taped to the inside of a kitchen cabinet. Write down that 300 ml = 10.14 oz. You'll thank yourself later when you're in the middle of a complex recipe and can't remember if you should be multiplying or dividing.