Speed Calculator

Calculate speed, distance or time — with unit conversions and real-world comparisons

Find Speed
h : m : s

Speed, Distance and Time

The speed-distance-time relationship is one of the most fundamental in physics. Knowing any two values allows you to calculate the third. The key is consistent units — always match the time units.

Formulas

Average vs Instantaneous Speed

This calculator computes average speed — total distance divided by total time. Instantaneous speed is the speed at a specific moment (what a speedometer shows). For non-uniform motion, average speed gives you the overall rate but not the details of the journey.

Note: Results use average speed over the given distance and time. Mach number is approximate — it varies with altitude and air temperature (sea level standard: 340.29 m/s).
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The Speed of Light
Why 299,792,458 m/s is the universe's speed limit — and the strange consequences of approaching it.
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// Quick Conversion

To convert km/h to m/s, divide by 3.6. To go the other way, multiply by 3.6. This comes from 1000 m/km ÷ 3600 s/hr.

// Mach Number

Mach 1 = the speed of sound ≈ 1235 km/h (768 mph) at sea level. It varies with temperature — at altitude it's lower.

// Light Speed

Light travels at 299,792,458 m/s. At that speed you could circle the Earth 7.5 times per second.

// Pace vs Speed

Runners use pace (min/km or min/mile) not speed. Pace = 60 ÷ speed (km/h). A 6 min/km pace = 10 km/h.