1 US teaspoon = 5 ml exactly. Multiply teaspoons by 5 to convert to millilitres.
| Teaspoon (tsp) | Millilitre (ml) |
|---|---|
| 0.25 tsp | 1.25 ml |
| 0.5 tsp | 2.5 ml |
| 1 tsp | 5 ml |
| 1.5 tsp | 7.5 ml |
| 2 tsp | 10 ml |
| 3 tsp | 15 ml |
| 4 tsp | 20 ml |
| 5 tsp | 25 ml |
| 6 tsp | 30 ml |
| 8 tsp | 40 ml |
The teaspoon is one of the most common measuring units in cooking, especially for spices, leaveners, and flavourings. The modern standard — used by US, UK, and most metric countries — is exactly 5 ml per teaspoon, making conversion to millilitres as simple as multiplying by 5.
Common fractional teaspoon measurements and their millilitre equivalents: ¼ tsp = 1.25 ml, ½ tsp = 2.5 ml, ¾ tsp = 3.75 ml, 1 tsp = 5 ml, 1½ tsp = 7.5 ml. These tiny volumes are often where baking precision is most critical — the wrong amount of baking soda or salt can noticeably affect the result.
For very small amounts (under 1 ml), kitchen scales are more reliable than small teaspoon fractions. Many digital scales resolve to 0.1 g, making them practical for measuring ¼ tsp of baking soda (≈ 1.5 g) or similar tiny quantities.
1 US teaspoon equals exactly 5 ml.
Half a teaspoon equals 2.5 ml.
Yes, the metric teaspoon used internationally is defined as 5 ml. The older US customary teaspoon was 4.92892 ml, but modern US recipes use the 5 ml metric definition. The difference is negligible in cooking.