How to convert US teaspoons to millilitres
One US teaspoon equals 4.9289 millilitres, so multiply the number of US teaspoons by 4.9289:
ml = tsp × 4.9289
tsp = ml ÷ 4.9289 (1 ml = 0.202884 tsp)
Example: 0.25 tsp → 0.25 × 4.9289 = 1.2322 ml.
Going the other way, divide by 4.9289, or multiply by 0.202884; the millilitres to US teaspoons converter does it for you.
Everyday values
| US teaspoons | Millilitres | For example |
|---|---|---|
| 0.25 tsp | 1.2322 ml | 1/4 teaspoon |
| 0.5 tsp | 2.4645 ml | 1/2 teaspoon |
| 1 tsp | 4.9289 ml | one teaspoon |
| 3 tsp | 14.7868 ml | one tablespoon |
When you need this conversion
A US teaspoon is 4.93 ml, usually rounded to 5 ml in metric recipes. Three teaspoons make one tablespoon. For medicines, use the syringe or cup that comes with the product: household spoons vary a lot in size.
US teaspoon to millilitre conversion table
| tsp | ml | tsp | ml |
|---|---|---|---|
| 0.25 tsp | 1.2322 ml | 2.25 tsp | 11.0901 ml |
| 0.5 tsp | 2.4645 ml | 2.5 tsp | 12.3223 ml |
| 0.75 tsp | 3.6967 ml | 2.75 tsp | 13.5545 ml |
| 1 tsp | 4.9289 ml | 3 tsp | 14.7868 ml |
| 1.25 tsp | 6.1612 ml | 3.25 tsp | 16.019 ml |
| 1.5 tsp | 7.3934 ml | 3.5 tsp | 17.2512 ml |
| 1.75 tsp | 8.6256 ml | 3.75 tsp | 18.4835 ml |
| 2 tsp | 9.8578 ml | 4 tsp | 19.7157 ml |
About the units
- US teaspoon (tsp): 1/3 US tablespoon, about 4.93 millilitres.
- Millilitre (ml): one thousandth of a litre, the same as one cubic centimetre.
Both are units of volume. The conversion factor comes from the exact definitions above, so the calculator is exact; results are only rounded for display (up to six significant digits).
Frequently asked questions
How many millilitres are in one US teaspoon?
One US teaspoon is 4.9289 millilitres. One millilitre is 0.202884 US teaspoons.
How do I convert US teaspoons to millilitres?
Multiply the value in US teaspoons by 4.9289. To go back, divide by 4.9289.
What is 0.25 tsp in millilitres?
0.25 tsp = 1.2322 ml.
What is 0.5 tsp in millilitres?
0.5 tsp = 2.4645 ml.
Sources
- NIST Special Publication 811 (2008), Guide for the Use of the International System of Units (SI), Appendix B: conversion factors.
- NIST Handbook 44 (2024), Appendix C: General tables of units of measurement.
Last reviewed 5 October 2026. Results are estimates; see our disclaimer.