You’re standing over a bowl of muffin batter. The recipe calls for five milliliters of vanilla extract, but all you have is a cluttered drawer of mismatched silverware. You grab a spoon. Any spoon. But then you pause because you remember that one time your cake tasted like a salt lick. It matters. A lot.
A teaspoon is how many ml exactly? If you want the quick, "I’m in the middle of cooking" answer: it is 4.92892 milliliters.
Most people just round that up to 5ml. In fact, if you buy a medicine dropper or a plastic measuring spoon in the United States, it’s going to be calibrated to exactly 5ml. But here is where it gets weird. Depending on where your recipe was written—be it a cozy cottage in London or a high-rise in New York—that "teaspoon" might not mean what you think it means.
The Global Confusion of the Humble Teaspoon
We like to think of measurements as universal truths, like gravity or the speed of light. They aren't. They’re historical accidents.
In the United States, we use the US Customary System. Here, a teaspoon is 1/6 of a fluid ounce. When you do the math to convert that to the metric system, you get that pesky 4.92ml figure. However, if you head over to the United Kingdom, Canada, or Australia, they’ve mostly embraced the metric teaspoon. A metric teaspoon is exactly 5ml. No decimals, no fuss.
Does that 0.08ml difference matter? Honestly, for a batch of chocolate chip cookies, no. You won't notice. But if you’re a pharmacist or a home chemist, that tiny margin of error starts to look a lot bigger.
Then there’s the Australian tablespoon, which is a total outlier. While most of the world agrees a tablespoon is three teaspoons (15ml), Australia decided a tablespoon should be four teaspoons (20ml). If you’re using an Aussie cookbook, your ratios are going to be wild if you don't adjust.
Why You Should Never Use a "Table" Spoon for Measuring
Let's talk about the spoons in your silverware drawer. You know the ones. The "small" ones you use for yogurt and the "big" ones you use for cereal.
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Never use these for baking. Just don't.
Standard dinnerware is designed for aesthetics and mouthfeel, not volume. I’ve seen "teaspoons" from IKEA that hold barely 3ml and antique silver spoons that hold nearly 7ml. If you’re making a delicate soufflé or a sourdough starter, using a literal spoon from your drawer is basically gambling with your dinner.
A study published in the International Journal of Clinical Practice found that when people used kitchen spoons to dose liquid medicine, they missed the mark by up to 20%. That’s the difference between a child getting better and a child ending up in the ER with an accidental overdose.
The Chemistry of 5ml: When Accuracy is Non-Negotiable
Cooking is an art, but baking? Baking is chemistry.
When you ask how many ml are in a teaspoon, you’re usually dealing with high-potency ingredients. Think baking soda, yeast, salt, or almond extract.
Take baking powder. It’s a leavening agent. If you use 6ml instead of 5ml because your "teaspoon" was a bit too deep, your cake might rise too fast, the bubbles will pop, and the whole thing will collapse into a dense, gummy mess. On the flip side, too little salt in bread isn't just a flavor issue; salt regulates the fermentation of yeast.
- Leavening agents: Small errors lead to structural failure.
- Essential oils/extracts: Overwhelming flavor profiles.
- Spices (like Cayenne): Can make a dish inedible.
- Medicinal liquids: Potential for toxicity or lack of efficacy.
Converting ml to Teaspoons on the Fly
Sometimes you’re looking at a bottle of cough syrup or a bottle of specialized fertilizer for your houseplants and it only lists milliliters. You need a mental shortcut.
Basically, think in increments of five.
2.5ml is a half teaspoon.
5ml is one teaspoon.
7.5ml is one and a half teaspoons.
10ml is two teaspoons.
15ml is a tablespoon.
It’s simple until you hit the weird numbers. If a recipe asks for 4ml, just underfill your 5ml spoon. It's not worth the headache of finding a syringe unless you’re working with something incredibly concentrated.
Liquid vs. Dry: The Teaspoon's Secret Life
Here is a nuance people often miss: milliliters measure volume, not weight.
A teaspoon of lead is going to weigh a lot more than a teaspoon of feathers, but they both occupy 5ml of space. However, in the kitchen, "dry" teaspoons are often "heaping" or "rounded."
When a scientist or a professional pastry chef talks about a teaspoon being 5ml, they are talking about a level spoon. They take a knife, they scrape it across the top, and they ensure the surface is flat. If you’re scooping flour and it’s mounded over the top, you aren't using 5ml. You’re likely using 7ml or 8ml.
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This is why the "teaspoon to ml" conversion is mostly a conversation about liquids. For dry ingredients, the world is moving toward grams because it's just more reliable.
The Medicine Cabinet Danger
If you take nothing else away from this, let it be this: throw away the kitchen spoon when it’s time for medicine.
Modern medicine is precise. Most pediatricians now recommend using oral syringes because they eliminate the "spoon" variable entirely. A "teaspoon" of Tylenol might be 160mg of the drug, but if your spoon is 20% too big, you’re putting a lot of strain on a small liver.
The FDA has actually issued guidance urging manufacturers to provide consistent dosing devices. They want the "ml" on the bottle to match the "ml" on the cup or syringe provided. It sounds obvious, but for decades, it wasn't the standard.
Practical Steps for a Precise Kitchen
If you want to stop guessing, there are a few things you can do right now.
First, buy a set of stainless steel measuring spoons that include the "ml" markings etched into the handle. Plastic ones are okay, but the markings rub off over time, and they can warp in the dishwasher. Look for a set that includes the 1/8 tsp (0.6ml) and 1/4 tsp (1.2ml) sizes.
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Second, if you’re serious about your results, get a digital scale. Most modern scales can toggle between grams and milliliters for water-based liquids.
Finally, check your source. If you’re using a vintage recipe from the 1940s, a "teaspoon" might have been a less standardized suggestion than a modern metric-calibrated tool.
Moving Forward With Confidence
To keep your cooking consistent, always assume a teaspoon is 5ml unless you are in a high-stakes laboratory setting.
- Level your spoons with a flat edge to ensure you aren't adding 20-30% more volume than intended.
- Keep a conversion chart inside your pantry door for quick reference between ml, tsp, and Tbsp.
- Use oral syringes for any liquid medication to ensure safety and accuracy.
- Trust your scale over your volume measurements for dry goods like salt and baking soda whenever possible.
By treating that little spoon like the precision instrument it's supposed to be, you’ll find your recipes become much more predictable and your "kitchen accidents" start to disappear.