Speed Converter
Runs locally in your browser. Nothing leaves your device.Enter one speed and instantly convert it to km/h, m/s, mph, knots, and other common units.
Use a comma or period as the decimal separator; do not use thousands separators.
All units
Metric and SI
Imperial and US customary
Nautical
Scientific reference
How it works
- 1
Enter value and source unit
Enter the speed value and choose the source unit.
- 2
Choose the target unit
Choose the target unit, even from a different group, for example from knots to km/h.
- 3
Copy the result or swap units
Copy one or all results, or swap the source and target unit for the next conversion.
Good to know
The speed converter converts directly in your browser between metric/SI, Anglo-American, and nautical units, via a common meters-per-second base. Knots use the international nautical mile (1 nmi = 1852 m), and c refers exclusively to the speed of light in a vacuum.
Calculation runs locally in the browser. Mach is deliberately not included because the local speed of sound depends on medium and temperature; navigation, aviation, and safety systems require authoritative instruments and standards regardless.
Typical use cases
Convert vehicle speeds between systems
Convert km/h to mph or vice versa, for example when comparing speedometer figures from different countries.
Interpret nautical and technical speeds
Convert knots to km/h or m/s, for example for sailing, shipping, or weather figures.
Use scientific speed references
Use c as a reference value for the speed of light in vacuum in physics calculations or comparisons.
Tips for better results
Mach is deliberately not included
Since the speed of sound depends on medium and temperature, there's no single fixed conversion factor for Mach — for Mach figures, use a source with the matching environmental conditions.
Use official instruments for safety-critical applications
For navigation, aviation, or safety systems, authoritative, calibrated instruments and standards apply — this converter serves general conversion, not safety-critical use.
Features
Three unit groups
Metric/SI, imperial, and nautical are cleanly separated.
Local conversion
Calculation happens directly in the browser, without transmission to a server.
Sign is preserved
Negative values are preserved as one-dimensional speed instead of being automatically converted to magnitudes.
Frequently asked questions
Why isn't Mach included?
Because the local speed of sound depends on medium and temperature, so there is no single fixed conversion factor.
Which nautical mile is used for knots?
The international nautical mile, where 1 nmi = 1852 m.
Are my inputs uploaded?
No. Conversion runs entirely locally in the browser.
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