# Kilometers per hour to Mach (sea level) (km/h to mach)

> Convert kilometers per hour to Mach (sea level): 1 km/h = 0.000816288 mach. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `kmh-to-mach` · Quantity: Speed (`speed`, base unit m/s) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/kmh-to-mach · This document: https://tttkmbb.com/conversion/kmh-to-mach.md · JSON: https://tttkmbb.com/conversion/kmh-to-mach.json (add `?value=` for a result)

## Formula

- `1 km/h = 0.000816288 mach`
- `Mach (sea level) = kilometers per hour × 0.0008162876153`
- Reverse: `kilometers per hour = Mach (sea level) × 1225.0584`

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 km/h = 0.00408144 mach
- 12.5 km/h = 0.0102036 mach
- 100 km/h = 0.0816288 mach

## Conversion table

| Kilometers per hour (km/h) | Mach (sea level) (mach) |
| --- | --- |
| 1 | 0.000816288 |
| 2 | 0.00163258 |
| 3 | 0.00244886 |
| 4 | 0.00326515 |
| 5 | 0.00408144 |
| 6 | 0.00489773 |
| 7 | 0.00571401 |
| 8 | 0.0065303 |
| 9 | 0.00734659 |
| 10 | 0.00816288 |
| 15 | 0.0122443 |
| 20 | 0.0163258 |
| 25 | 0.0204072 |
| 30 | 0.0244886 |
| 40 | 0.0326515 |
| 50 | 0.0408144 |
| 75 | 0.0612216 |
| 100 | 0.0816288 |
| 200 | 0.163258 |
| 250 | 0.204072 |
| 500 | 0.408144 |
| 1000 | 0.816288 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=km%2Fh&to_unit=mach` → 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":"km/h","to_unit":"mach"}`
- All speed units: https://tttkmbb.com/api/v1/units?quantity=speed · full converter: [Speed Converter](https://tttkmbb.com/conversion/speed.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many Mach (sea level) are in one kilometer per hour?**

1 km/h = 0.000816288 mach. 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 kilometers per hour to Mach (sea level)?**

Multiply the value in kilometers per hour by 0.0008162876153: Mach (sea level) = kilometers per hour × 0.0008162876153. For example, 5 km/h = 0.00408144 mach.

**How do I convert Mach (sea level) back to kilometers per hour?**

Multiply by the inverse factor 1225.0584 (kilometers per hour = Mach (sea level) × 1225.0584), or use the Mach (sea level)-to-kilometers per hour page.

## Related conversions

- [Mach (sea level) to kilometers per hour](https://tttkmbb.com/conversion/mach-to-kmh.md) (reverse)
- [Kilometers per hour to Miles per hour](https://tttkmbb.com/conversion/kmh-to-mph.md)
- [Miles per hour to Kilometers per hour](https://tttkmbb.com/conversion/mph-to-kmh.md)
- [Meters per second to Kilometers per hour](https://tttkmbb.com/conversion/meters-per-second-to-kmh.md)
- [Kilometers per hour to Meters per second](https://tttkmbb.com/conversion/kmh-to-meters-per-second.md)
- [Meters per second to Miles per hour](https://tttkmbb.com/conversion/meters-per-second-to-mph.md)
- [Miles per hour to Meters per second](https://tttkmbb.com/conversion/mph-to-meters-per-second.md)
- [Knots to Kilometers per hour](https://tttkmbb.com/conversion/knots-to-kmh.md)
- [Kilometers per hour to Knots](https://tttkmbb.com/conversion/kmh-to-knots.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)