# Stone to Kilograms (st to kg)

> Convert stone to kilograms: 1 st = 6.35029 kg. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `stone-to-kg` · Quantity: Mass (`mass`, base unit kg) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/stone-to-kg · This document: https://tttkmbb.com/conversion/stone-to-kg.md · JSON: https://tttkmbb.com/conversion/stone-to-kg.json (add `?value=` for a result)

## Formula

- `1 st = 6.35029 kg`
- `kilograms = stone × 6.35029318`
- Reverse: `stone = kilograms × 0.1574730444`

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 st = 31.7515 kg
- 12.5 st = 79.3787 kg
- 100 st = 635.029 kg

## Conversion table

| Stone (st) | Kilograms (kg) |
| --- | --- |
| 1 | 6.35029 |
| 2 | 12.7006 |
| 3 | 19.0509 |
| 4 | 25.4012 |
| 5 | 31.7515 |
| 6 | 38.1018 |
| 7 | 44.4521 |
| 8 | 50.8023 |
| 9 | 57.1526 |
| 10 | 63.5029 |
| 15 | 95.2544 |
| 20 | 127.006 |
| 25 | 158.757 |
| 30 | 190.509 |
| 40 | 254.012 |
| 50 | 317.515 |
| 75 | 476.272 |
| 100 | 635.029 |
| 200 | 1270.06 |
| 250 | 1587.57 |
| 500 | 3175.15 |
| 1000 | 6350.29 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=st&to_unit=kg` → 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":"st","to_unit":"kg"}`
- All mass units: https://tttkmbb.com/api/v1/units?quantity=mass · full converter: [Mass / Weight Converter](https://tttkmbb.com/conversion/mass.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many kilograms are in one stone?**

1 st = 6.35029 kg. 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 stone to kilograms?**

Multiply the value in stone by 6.35029318: kilograms = stone × 6.35029318. For example, 5 st = 31.7515 kg.

**How do I convert kilograms back to stone?**

Multiply by the inverse factor 0.1574730444 (stone = kilograms × 0.1574730444), or use the kilograms-to-stone page.

## Related conversions

- [Kilograms to stone](https://tttkmbb.com/conversion/kg-to-stone.md) (reverse)
- [Kilograms to Pounds](https://tttkmbb.com/conversion/kg-to-lbs.md)
- [Pounds to Kilograms](https://tttkmbb.com/conversion/lbs-to-kg.md)
- [Grams to Ounces](https://tttkmbb.com/conversion/grams-to-oz.md)
- [Ounces to Grams](https://tttkmbb.com/conversion/oz-to-grams.md)
- [Pounds to Ounces](https://tttkmbb.com/conversion/lbs-to-oz.md)
- [Ounces to Pounds](https://tttkmbb.com/conversion/oz-to-lbs.md)
- [Kilograms to Grams](https://tttkmbb.com/conversion/kg-to-grams.md)
- [Grams to Kilograms](https://tttkmbb.com/conversion/grams-to-kg.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)