How do you convert km/h to mph?

Multiply km/h by 0.621371 to get mph, or divide mph by 0.621371 to go back. For example, 200 km/h × 0.621371 ≈ 124.3 mph. The factor comes from one mile equalling 1.609344 kilometres.

How do you convert to metres per second?

Divide km/h by 3.6 to get m/s, since one hour is 3600 seconds and one kilometre is 1000 metres. So 200 km/h ÷ 3.6 ≈ 55.6 m/s. To convert mph to m/s, multiply by 0.44704.

What is a fast tennis serve?

ATP men's first serves average roughly 185 km/h (115 mph) and WTA women's first serves average roughly 160 km/h (100 mph). Serves above 210 km/h (130 mph) are elite, and the recorded men's record is about 263 km/h (163 mph).

Why are serve speeds quoted differently at events?

Most tournaments outside North America display km/h, while events in the United States usually display mph, which is why the same serve looks like 200 in Australia and 124 at the US Open. This converter lets you compare them on equal footing.

Is radar speed the speed off the racquet?

Serve radar measures the ball's peak speed just after impact, before air resistance slows it. By the time the ball reaches the returner it has lost a substantial fraction of that speed, so the radar number is the launch speed, not the speed at the baseline.

Tennis Serve Speed Converter

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Serve speeds are quoted in km/h at most tournaments and mph in the United States, which makes comparing players awkward. This converter turns any serve speed into all three common units — km/h, mph, and m/s — and shows where it sits against ATP and WTA benchmarks.

How it works

The conversions use exact factors derived from the definition of a mile and an hour:

mph  = kmh × 0.621371
m/s  = kmh ÷ 3.6
kmh  = mph ÷ 0.621371 = mph × 1.609344
m/s  = mph × 0.44704

Enter a speed in any unit and the tool normalises it to km/h internally, then converts out to the other two so all three always agree.

Example and tips

A 200 km/h serve converts to 200 × 0.621371 ≈ 124.3 mph and 200 ÷ 3.6 ≈ 55.6 m/s — a strong tour-level first serve. Remember radar shows the speed right off the strings; the ball is noticeably slower by the time it crosses the net, so reaction time depends on more than the headline number.