Speed Converter

What this tool does

Speed Converter switches between road, aviation, marine and scientific speed units with exact factors. A pace panel also turns any speed into minutes per kilometre or mile and finish times for common race distances.

Speed limits are posted in km/h or mph depending on the country, ships and aircraft use knots, physics problems use metres per second and runners think in minutes per kilometre. A misread unit can mean a speeding ticket abroad or a badly planned training run.

This tool converts through metres per second using exact definitions: 1 km/h is 1/3.6 m/s, 1 mph is 0.44704 m/s and 1 knot is one nautical mile (1,852 m) per hour, about 0.5144 m/s. Mach is approximate by nature because the speed of sound depends on air temperature; the tool uses 340.294 m/s, the International Standard Atmosphere value at sea level. The Speed to pace panel inverts a speed into time per distance. Everything is calculated locally as you type.

How to use Speed Converter

1. Enter a speed in the Value field.
2. Choose the From and To units, for example Kilometre per hour and Mile per hour.
3. Read the Result, copy it, or swap the units with the arrow button.
4. Check the table to see the speed in all units at once.
5. In Speed to pace, enter a running or cycling speed to see time per kilometre, per mile and for 5 km to marathon distances.
6. Use Batch convert for a list of speeds, such as a set of speed limits.

Tips for better results

• To estimate mph from km/h, multiply by 0.62; 100 km/h is about 62 mph.
• To get m/s from km/h, divide by 3.6; 90 km/h is exactly 25 m/s.
• A knot is about 1.15 mph, so a 20-knot boat travels at about 23 mph.
• Pace is the inverse of speed: running at 12 km/h means 5:00 per kilometre.

Common use cases

• Understanding speed limits and car speedometers when driving abroad.
• Converting wind speeds between knots, km/h and m/s from weather reports.
• Turning treadmill speeds into running pace for race planning.
• Solving physics homework that mixes m/s and km/h.

Common mistakes to avoid

• Treating Mach as a fixed speed; Mach 1 at high altitude is much slower than at sea level.
• Converting km/h to m/s by multiplying by 3.6 instead of dividing.
• Using statute miles per hour when a nautical source means knots.