# US teaspoons to Milliliters (tsp to mL)

> Convert US teaspoons to milliliters: 1 tsp = 4.92892 mL. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `teaspoons-to-ml` · Quantity: Volume (`volume`, base unit L) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/teaspoons-to-ml · This document: https://tttkmbb.com/conversion/teaspoons-to-ml.md · JSON: https://tttkmbb.com/conversion/teaspoons-to-ml.json (add `?value=` for a result)

## Formula

- `1 tsp = 4.92892 mL`
- `milliliters = US teaspoons × 4.928921594`
- Reverse: `US teaspoons = milliliters × 0.2028841362`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 tsp = 24.6446 mL
- 12.5 tsp = 61.6115 mL
- 100 tsp = 492.892 mL

## Conversion table

| US teaspoons (tsp) | Milliliters (mL) |
| --- | --- |
| 1 | 4.92892 |
| 2 | 9.85784 |
| 3 | 14.7868 |
| 4 | 19.7157 |
| 5 | 24.6446 |
| 6 | 29.5735 |
| 7 | 34.5025 |
| 8 | 39.4314 |
| 9 | 44.3603 |
| 10 | 49.2892 |
| 15 | 73.9338 |
| 20 | 98.5784 |
| 25 | 123.223 |
| 30 | 147.868 |
| 40 | 197.157 |
| 50 | 246.446 |
| 75 | 369.669 |
| 100 | 492.892 |
| 200 | 985.784 |
| 250 | 1232.23 |
| 500 | 2464.46 |
| 1000 | 4928.92 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=tsp&to_unit=mL` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"tsp","to_unit":"mL"}`
- All volume units: https://tttkmbb.com/api/v1/units?quantity=volume · full converter: [Volume Converter](https://tttkmbb.com/conversion/volume.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many milliliters are in one teaspoon?**

1 tsp = 4.92892 mL. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert US teaspoons to milliliters?**

Multiply the value in US teaspoons by 4.928921594: milliliters = US teaspoons × 4.928921594. For example, 5 tsp = 24.6446 mL.

**How do I convert milliliters back to US teaspoons?**

Multiply by the inverse factor 0.2028841362 (US teaspoons = milliliters × 0.2028841362), or use the milliliters-to-US teaspoons page.

## Related conversions

- [Milliliters to US teaspoons](https://tttkmbb.com/conversion/ml-to-teaspoons.md) (reverse)
- [Liters to US gallons](https://tttkmbb.com/conversion/liters-to-gallons.md)
- [US gallons to Liters](https://tttkmbb.com/conversion/gallons-to-liters.md)
- [Milliliters to US fluid ounces](https://tttkmbb.com/conversion/ml-to-fl-oz.md)
- [US fluid ounces to Milliliters](https://tttkmbb.com/conversion/fl-oz-to-ml.md)
- [Liters to Milliliters](https://tttkmbb.com/conversion/liters-to-ml.md)
- [Milliliters to Liters](https://tttkmbb.com/conversion/ml-to-liters.md)
- [US cups to Milliliters](https://tttkmbb.com/conversion/cups-to-ml.md)
- [Milliliters to US cups](https://tttkmbb.com/conversion/ml-to-cups.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)