Speed Converter – km/h, mph, Knots and m/s

How speed units relate

Speed is distance divided by time, so each unit combines a length and a time unit. The converter works through metres per second:

• 1 km/h = 1,000 m ÷ 3,600 s = 0.27778 m/s
• 1 mph = 1,609.344 m ÷ 3,600 s = 0.44704 m/s
• 1 knot = 1,852 m ÷ 3,600 s = 0.51444 m/s
• 1 ft/s = 0.3048 m/s

That means 1 mph is exactly 1.609344 km/h and 1 knot is exactly 1.852 km/h.

Where each unit is used

• km/h – road signs and car speedometers in most countries.
• mph – road speeds in the United States and the United Kingdom.
• Knots – ships, aircraft and wind speeds in marine and aviation forecasts.
• m/s – physics, engineering and many weather services for wind speed.
• ft/s – ballistics, engineering and some sports measurements in the US.

Common speed limits

A 50 km/h city limit is about 31 mph, 100 km/h is 62 mph and 130 km/h is 81 mph. In the other direction, 30 mph is 48 km/h, 60 mph is 97 km/h and 70 mph is 113 km/h. Driving abroad with a speedometer in the other unit is a common reason to convert, so it helps to remember that a speed in mph is roughly 60% of the same value in km/h.

Converting m/s to km/h quickly

Multiply metres per second by 3.6 to get kilometres per hour; divide km/h by 3.6 to get m/s. A sprinter at 10 m/s runs 36 km/h, and a 72 km/h wind is 20 m/s.

Running pace versus speed

Runners often use pace – minutes per kilometre or per mile – instead of speed. Pace is the inverse of speed: 12 km/h equals 5:00 min/km. Use the running pace calculator to convert between pace, speed and finishing times.

Sources

Conversion factors follow the SI definitions in the BIPM SI Brochure and the exact factors for US customary and imperial units in NIST Special Publication 811.