Speed Converter
Convert km/h, mph, metres per second and knots instantly using exact factors. Compare Australian speed limits with overseas speeds.
Your results
Calculation breakdown
- Conversion
- Result = value × (from unit's km/h) ÷ (to unit's km/h)
- Common factors
- 1 mph = 1.609344 km/h; 1 m/s = 3.6 km/h; 1 kn = 1.852 km/h
Worked example
A 100 km/h speed limit is approximately 62.1371 miles per hour, and a 110 km/h freeway limit is about 30.5556 metres per second.
Assumptions
- Uses exact conversion factors based on the international mile and nautical mile.
- Results are shown to six significant figures.
How this calculator works
This calculator converts a speed value between kilometres per hour, miles per hour, metres per second and knots. Kilometres per hour is the standard unit on Australian speedometers and speed limit signs, while miles per hour and knots are useful for comparing overseas vehicles, aircraft or marine speeds.
Converting Australian speed limits and overseas speeds
Australian speed signs and speedometers use kilometres per hour, while the United States and United Kingdom use miles per hour for road speeds. One mile is exactly 1.609344 kilometres, so the converter divides km/h by that factor to get mph and multiplies to go the other way.
Metres per second is common in science and sport, and knots are used for boating, aviation and marine wind forecasts. One knot is one nautical mile per hour, which is exactly 1.852 kilometres per hour.
- 50 km/h ≈ 31.07 mph
- 100 km/h ≈ 62.14 mph
- 110 km/h ≈ 68.35 mph
- 1 m/s = 3.6 km/h
- 1 knot = 1.852 km/h
Use converted speeds as a reference only
A unit conversion does not change the legal speed limit that applies to a road. Always follow posted signs, your speedometer and the road rules of the state, territory or country where you are driving.
Speedometers and GPS apps can show slightly different speeds because of tyre size, calibration and signal accuracy. Results here are shown to six significant figures, which is more precise than any vehicle display.
Frequently asked questions
What speed unit is used on Australian roads?
Australian speed limits and speedometers use kilometres per hour (km/h) as the standard unit.
How do knots relate to km/h?
One knot equals one nautical mile per hour, which is approximately 1.852 kilometres per hour, commonly used in aviation and boating.
Can I convert an American car's mph speedo to km/h?
Yes, select miles per hour as the source unit and kilometres per hour as the target for an instant conversion.
Content responsibility
Maintained by CalcAussie and last updated 15 October 2026. Checks applied: calculation method, worked examples, Australian terminology, material assumptions, official references where an external rule applies, and user-facing limitations.
Calculator results remain estimates based on the figures entered. Check material decisions against current official information and report a suspected error so it can be reproduced and corrected.