Physics class has a strict dress code: speeds must be in meters per second. But speedometers, weather reports, and sports broadcasts all speak kilometers per hour, so every dynamics problem starts with a conversion — divide by 3.6. The 3.6 comes from the 3,600 seconds in an hour divided by the 1,000 meters in a kilometer. A car at 36 km/h is doing exactly 10 m/s. Highway speed at 108 km/h is 30 m/s. The factor is clean enough that teachers expect you to do it by hand, and common enough that memorizing it pays off all semester.

Type your speed in the km/h box and the m/s readout divides by 3.6, with a bonus mph column at 0.621371 each. The 36 km/h example is the textbook anchor: exactly 10 m/s, the number in a thousand worked examples. The dramatic one is 1,235 km/h — the speed of sound at sea level — which becomes about 343 m/s, the Mach 1 figure every aerospace fan knows. Sprinters hit about 10 m/s (36 km/h) at top speed; a pitched baseball crosses the plate near 40 m/s. Students checking homework, engineers sizing ventilation airflow, and athletes analyzing GPS data all divide by 3.6 daily. Going the other way, multiply m/s by 3.6 — a 5 m/s wind is a breezy 18 km/h.

With the pre-filled defaults — km/h 36 — the km/h to m/s returns m/s 10.000000, mph 22.3694. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.