Speed Calculator

What do you want to solve?

How it works

One relationship ties all three quantities together: speed = distance ÷ time. Rearranged, distance = speed × time and time = distance ÷ speed. The calculator converts everything to kilometers and hours first, solves, then converts the answer into the units people use: 1 mile = 1.609344 km exactly, km/h ÷ 3.6 = m/s, and mph = km/h ÷ 1.609344.

Average, not instant: the speed here is an average over the whole distance — a trip with stops, traffic, or a fast start and slow finish still averages out to one number. That is exactly what you want for trip planning and training logs, and why it will differ from a speedometer snapshot.

Pace is speed turned inside out: time per unit distance instead of distance per unit time. Pace per km = total minutes ÷ kilometers; pace per mile = total minutes ÷ miles. Runners plan with pace because it answers "how fast is each mile?" directly.

Worked example: 100 miles in 2 hours is an average of 50 mph — which is 80.47 km/h, or 22.35 m/s, at a pace of 1:12 per mile (0:45 per km). A more typical running example: 10 km in 50 minutes is a pace of 5:00 per km (8:03 per mile).

Frequently asked questions

How do I convert mph to km/h? Multiply by 1.609344 (60 mph ≈ 96.6 km/h). For m/s, divide km/h by 3.6 (100 km/h ≈ 27.8 m/s). The result above always shows all three, so no separate conversion is needed.

Can this solve a marathon time? Yes — choose "solve for time," enter 26.2 miles (or 42.195 km) and your speed, or enter your finish time and solve for the average speed and pace you held.

Why is my pace per mile slower than per km? A mile is longer than a kilometer, so covering one takes more time at the same speed — the per-mile pace is always the bigger number.