There are 4.9 ml in a US teaspoon, and 5 ml in a metric teaspoon. Both answers are correct, and the difference is so small — about 1 percent — that it does not matter in cooking. A US teaspoon holds 4.93 ml, which is usually rounded to 4.9 ml, and a metric teaspoon holds exactly 5 ml. If a recipe calls for 2 teaspoons of vanilla, that is about 10 ml either way. This page gives you the table, the examples, and the warning that matters: never use a kitchen teaspoon for medicine, because a cutlery teaspoon can hold anywhere from 3 to 7 ml.
The conversion table
| Teaspoons | US millilitres | Metric millilitres | Tablespoons | Cups |
|---|---|---|---|---|
| 1/4 tsp | 1.2 ml | 1.25 ml | 1/12 tbsp | 1/192 cup |
| 1/2 tsp | 2.5 ml | 2.5 ml | 1/6 tbsp | 1/96 cup |
| 1 tsp | 4.9 ml | 5 ml | 1/3 tbsp | 1/48 cup |
| 2 tsp | 9.9 ml | 10 ml | 2/3 tbsp | 1/24 cup |
| 3 tsp | 14.8 ml | 15 ml | 1 tbsp | 1/16 cup |
| 4 tsp | 19.7 ml | 20 ml | 1 1/3 tbsp | 1/12 cup |
| 6 tsp | 29.6 ml | 30 ml | 2 tbsp | 1/8 cup |
| 12 tsp | 59.1 ml | 60 ml | 4 tbsp | 1/4 cup |
| 24 tsp | 118.3 ml | 120 ml | 8 tbsp | 1/2 cup |
| 48 tsp | 236.6 ml | 240 ml | 16 tbsp | 1 cup |
The US column is rounded to one decimal place. The metric column is exact, because a metric teaspoon is defined as 5 ml.
Worked example 1: vanilla extract in a cake
A cake recipe calls for 2 teaspoons of vanilla extract, and your measuring jug is marked in millilitres. Two teaspoons is 9.9 ml, so measure 10 ml. For vanilla, you can round to the nearest millilitre without any harm, because vanilla is forgiving and a drop more or less will not change the cake. The conversion is more useful in the other direction: a European recipe calls for 5 ml of vanilla, and you want to know how many teaspoons that is. Five millilitres is exactly 1 metric teaspoon, and it is 1.01 US teaspoons, so one level teaspoon is the right measure.
Worked example 2: baking powder, where precision matters
A muffin recipe calls for 1 teaspoon of baking powder, which is 4.9 ml. If you measure 5 ml, you have the right amount. If you measure a heaped teaspoon from the drawer, you might have 7 ml, which is nearly half as much again, and the muffins will rise too fast, then collapse, with a bitter taste. The lesson is that a teaspoon is a precise measure only when you use a proper measuring spoon and level it with the back of a knife. For baking powder, baking soda, and yeast, the millilitre figure is a reminder that a small error is a large percentage error, and that is why a scale is better for a large batch.
Worked example 3: a recipe written in millilitres only
A European spice blend recipe calls for 10 ml of paprika, 5 ml of cumin, and 5 ml of salt. Ten millilitres is 2 teaspoons, and 5 ml is 1 teaspoon, so the recipe is 2 teaspoons of paprika, 1 teaspoon of cumin, and 1 teaspoon of salt. European recipes are often written in multiples of 5 ml precisely because 5 ml is a teaspoon, and converting them is a matter of dividing by five. If you see a recipe that calls for 7.5 ml, it was written as 1 1/2 teaspoons, and you can measure it with a half-teaspoon measure.
Method and source
A US teaspoon is defined as one third of a US tablespoon, which is one sixth of a US fluid ounce, and a US fluid ounce is 29.5735 millilitres, so a US teaspoon is 4.9289 millilitres, usually rounded to 4.9 ml. A metric teaspoon is defined as exactly 5 millilitres. The two are so close that they can be swapped in cooking without any noticeable difference — the gap is 0.07 ml, which is less than a drop. The teaspoon is the smallest unit in the American system, and it is used for ingredients that are potent in small amounts: salt, baking powder, baking soda, yeast, spices, and vanilla. The metric teaspoon is the same idea in the metric system, and the two agree to within 1 percent.
Practical guidance
Use proper measuring spoons, not cutlery. A teaspoon from the drawer can hold anywhere from 3 to 7 ml, which is a variation of more than 100 percent on a small amount, and that will ruin a batch of baking. Buy a set that includes 1/4 teaspoon, 1/2 teaspoon, and 1 teaspoon, and level dry ingredients with the back of a knife. When a recipe gives an amount in millilitres that is a multiple of 5, convert it to teaspoons — 5 ml is a teaspoon, 10 ml is two, 15 ml is three — because a spoon is easier and more accurate than a jug for small amounts. And never use a kitchen teaspoon for medicine: use the dosing device that came with the bottle, because the millilitre figure on the label is the one that matters.
Frequently asked questions
How many millilitres are in 1 teaspoon?
There are 4.9 ml in 1 US teaspoon, and 5 ml in 1 metric teaspoon. The difference is about 1 percent, which does not matter in cooking. Use 5 ml as a round figure unless the recipe needs precision.
How many millilitres are in 2 teaspoons?
There are 9.9 ml in 2 US teaspoons, and 10 ml in 2 metric teaspoons. For most cooking, 10 ml is the figure to use, and it is the number you will see printed on most measuring jugs.
How many teaspoons are in 5 ml?
There is 1 teaspoon in 5 ml. Five millilitres is the definition of a metric teaspoon, and it is very close to a US teaspoon, which is 4.9 ml, so one teaspoon is the right measure either way.
Is a teaspoon 5 ml everywhere?
Almost. A metric teaspoon is 5 ml, and a US teaspoon is 4.9 ml, which is close enough to call 5 ml in cooking. The difference is 0.07 ml, which is less than a drop, so you can treat them as the same.
How many millilitres are in half a teaspoon?
There are 2.5 ml in half a teaspoon, in both the US and the metric system. Half a teaspoon is also a sixth of a tablespoon, and it is a common amount for baking soda and salt in a small batch.
Can I use a kitchen teaspoon to measure medicine?
No. Use the dosing spoon, cup, or syringe that came with the medicine. A kitchen teaspoon can hold anywhere from 3 to 7 ml, and that variation is dangerous for a dose. The millilitre figure on the bottle is the one to trust, measured with a proper device.