# US teaspoons to milliliters converter

> Convert US teaspoons to milliliters (teaspoons to ml) with the exact factor, a conversion chart and worked steps.

Interactive version: https://www.calcopenly.com/conversion/teaspoons-to-ml
Subject: Unit converters

Teaspoon quantities are useful when a recipe calls for a small amount and only a larger measure is available. Enter fractions precisely and check the US measuring-spoon convention. Ordinary cutlery is not a calibrated measuring tool.

One US teaspoon is exactly 4.9289215938 milliliters, so 1 tsp is 4.928922 mL. To convert teaspoons to ml, multiply by 4.9289215938; to convert back, multiply by 0.2028841362.

The US teaspoon is a third of a tablespoon, exactly 4.92892159375 mL. Because both units are defined exactly, the factor above is exact and the results here carry no conversion error.

## Inputs

- **US teaspoons (tsp)**

## Results

- Milliliters (mL) — main result
- Conversion
- 1 mL in US teaspoons (tsp)

## Formula

$$
\text{milliliters} = \text{US teaspoons} \times 4.92892159375
$$

## Worked examples

### 1 tsp to mL

- US teaspoons (tsp): 1 tsp
- **Milliliters: 4.92892159375 mL**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

### 4 tsp to mL

- US teaspoons (tsp): 4 tsp
- **Milliliters: 19.715686375 mL**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

### 0.25 tsp to mL

- US teaspoons (tsp): 0.25 tsp
- **Milliliters: 1.23223039844 mL**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

## Questions

### When would I convert teaspoons to ml?

Teaspoon quantities are useful when a recipe calls for a small amount and only a larger measure is available. Enter fractions precisely and check the US measuring-spoon convention. Ordinary cutlery is not a calibrated measuring tool.

### How many milliliters are in a US teaspoon?

One US teaspoon is exactly 4.9289215938 milliliters. The US teaspoon is a third of a tablespoon, exactly 4.92892159375 mL.

### How do you convert teaspoons to ml?

Multiply the number of US teaspoons by 4.9289215938. For example, 1 tsp × 4.9289215938 = 4.928922 mL. To go the other way, divide by 4.9289215938.

### How can I estimate teaspoons to ml without a calculator?

Multiply by 5. That is 1.4% high of the exact factor 4.9289215938, so 1 tsp comes out as 5 mL instead of 4.9289.

### How accurate is the US teaspoons to milliliters converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “1 tsp to mL” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

### Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.

## Sources

- [NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C: General tables of units of measurement](https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-44)
- [BIPM, The International System of Units (SI Brochure), 9th edition](https://www.bipm.org/en/publications/si-brochure)