Kilometres per hour to metres per second (km/h to m/s)

The formula

m/s = km/h × 0.2777777778

Where the factor comes from — each unit by its definition, then its size in SI:

• 1 km/h = km / h = 0.277777777778 m/s
• 1 m/s is the SI unit of speed.

Dividing the two SI sizes gives the factor: 0.277777777778 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 3.6.

Kinematics and energy formulas need speed in metres per second. Road speeds come in km/h or mph, so convert before you square anything: kinetic energy goes with v², so a unit slip is squared too.

Worked examples

• Motorway driving: 100 km/h = 27.7778 m/s — 100 × 0.2777777778 = 27.7778
• A brisk walk: 5 km/h = 1.38889 m/s — 5 × 0.2777777778 = 1.38889
• US highway driving (60 mph): 96.5606 km/h = 26.8224 m/s — 96.5606 × 0.2777777778 = 26.8224
• A hard-thrown ball: 108 km/h = 30 m/s — 108 × 0.2777777778 = 30

Frequently asked questions