# Pounds to Kilograms (lb to kg)

> Convert pounds to kilograms: 1 lb = 0.453592 kg. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 lb = 0.453592 kg`
- `kilograms = pounds × 0.45359237`
- Reverse: `pounds = kilograms × 2.204622622`

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 lb = 2.26796 kg
- 12.5 lb = 5.6699 kg
- 100 lb = 45.3592 kg

## Conversion table

| Pounds (lb) | Kilograms (kg) |
| --- | --- |
| 1 | 0.453592 |
| 2 | 0.907185 |
| 3 | 1.36078 |
| 4 | 1.81437 |
| 5 | 2.26796 |
| 6 | 2.72155 |
| 7 | 3.17515 |
| 8 | 3.62874 |
| 9 | 4.08233 |
| 10 | 4.53592 |
| 15 | 6.80389 |
| 20 | 9.07185 |
| 25 | 11.3398 |
| 30 | 13.6078 |
| 40 | 18.1437 |
| 50 | 22.6796 |
| 75 | 34.0194 |
| 100 | 45.3592 |
| 200 | 90.7185 |
| 250 | 113.398 |
| 500 | 226.796 |
| 1000 | 453.592 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=lb&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":"lb","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 pound?**

1 lb = 0.453592 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 pounds to kilograms?**

Multiply the value in pounds by 0.45359237: kilograms = pounds × 0.45359237. For example, 5 lb = 2.26796 kg.

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

Multiply by the inverse factor 2.204622622 (pounds = kilograms × 2.204622622), or use the kilograms-to-pounds page.

## Related conversions

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