Speed Converter
A speed converter changes a velocity between units such as kilometers per hour, miles per hour, meters per second and knots. Exact definitions apply: 1 mph = 1.609344 km/h and 1 knot = 1.852 km/h. This tool updates as you type and also gives an approximate Mach number based on the speed of sound at sea level.
Free, no signup. Runs entirely in your browser; files and text are not uploaded.
How to use the Speed Converter
- Enter the speed in the Value box.
- Choose the unit you have in From, such as km/h.
- Choose the unit you want in To, such as mph.
- Read or copy the result, or use a preset such as mph → km/h.
Features
- km/h, mph, m/s, ft/s, knots, km/s and Mach
- Exact factors: 1 mph = 0.44704 m/s, 1 knot = 1852/3600 m/s
- Mach based on the standard-atmosphere sea-level speed of sound (340.29 m/s)
- All-units table, presets, swap and copy buttons
Frequently asked questions
How do I convert km/h to mph?
Divide km/h by 1.609344. For example, 100 km/h is about 62.137 mph.
How fast is a knot?
One knot is one nautical mile per hour: exactly 1.852 km/h, or about 1.15078 mph.
How fast is Mach 1?
Mach 1 is the local speed of sound, so it changes with air temperature. At sea level in the standard atmosphere (15 °C) it is about 340.29 m/s or 1,225 km/h.
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Built and reviewed by Naqash Thaheem, Technical Project Manager. Last reviewed 2026-09-24.