Tennis Serve Speed Calculator
This calculator converts tennis serve speed between miles per hour and kilometers per hour, and estimates how long the ball takes to travel from the server to the returner's baseline. Understanding serve flight time puts serve speed in context: even a small increase in speed meaningfully reduces the time available for the returner to react. The flight time calculation uses a standard service distance of 18 meters, which represents the approximate ball travel distance from the server's contact point to the returner's position near the baseline. This is consistent with ITF court dimension data: the baseline-to-baseline court length is 23.77 meters, the net bisects the court, and the service box extends 6.40 meters from the net toward the receiver. Ball flight in reality is not purely horizontal (the ball curves and decelerates due to air resistance and spin), so this calculator gives a straight-line minimum flight time. The comparison benchmarks shown (average ATP first serve approximately 193 km/h, average WTA first serve approximately 161 km/h, fastest ever 263 km/h by Sam Groth) are based on published professional data.
120 mph = -- km/h | Ball flight time: -- ms
How serve speed and flight time are calculated
Speed conversion: km/h = mph x 1.60934
Speed in m/s = km/h / 3.6
Flight time (seconds) = 18 / speed_ms
Flight time (milliseconds) = flight time (s) x 1,000
Worked example
Serve speed 120 mph:
- km/h = 120 x 1.60934 = 193.12 km/h
- m/s = 193.12 / 3.6 = 53.64 m/s
- Flight time = 18 / 53.64 = 0.3356 s = 335.6 ms
For context, average human visual reaction time is approximately 150 to 200 ms, leaving the returner only about 100 to 180 ms to execute their shot against a 120 mph serve.
Professional serve speed reference
| Benchmark | km/h | mph | Flight time (18 m) |
|---|---|---|---|
| All-time record (Sam Groth, 2012) | 263 | 163.4 | ~246 ms |
| ATP average 1st serve | 193 | 119.9 | ~335 ms |
| WTA average 1st serve | 161 | 100.0 | ~402 ms |
| Club player (strong) | 160 | 99.4 | ~405 ms |
| Club player (average) | 120 | 74.6 | ~540 ms |
| Beginner | 80 | 49.7 | ~810 ms |
Flight times are approximate straight-line estimates. Air resistance and ball spin reduce actual in-flight speed during the trajectory.
Tennis serve speed: frequently asked questions
What is considered a fast tennis serve?
On the ATP Tour, average first serve speeds are typically in the range of 190 to 205 km/h (118 to 127 mph), with top servers regularly exceeding 220 km/h (137 mph). On the WTA Tour, average first serves run around 155 to 170 km/h (96 to 106 mph). For recreational players, anything above 160 km/h (100 mph) is considered strong. Second serves are typically 30 to 50 km/h slower than first serves to ensure reliability over placement.
How is serve speed measured with radar?
Tournament serve speeds are measured using Doppler radar guns positioned behind the server's baseline or in the serve box area. The radar measures the ball's speed immediately after contact with the racket, when the ball is moving fastest. The ITF specifies standards for speed measurement equipment used at professional tournaments. Consumer radar guns and smart tennis ball systems (such as connected rackets) provide similar measurements but may have lower accuracy than tournament-grade equipment.
Why does serve speed matter in tennis?
Serve speed directly reduces the time the returner has to react and move into position. At 200 km/h, a serve travels the 18 meters from server to returner's baseline in approximately 0.32 seconds. Research on human reaction times shows that visual processing alone takes around 0.15 to 0.20 seconds, leaving very little time for the returner to execute a full swing. This is why elite servers can win free points even when the serve is not placed in a difficult location.
What is the fastest serve ever recorded?
The fastest serve in professional tennis was recorded by Sam Groth of Australia at 263.0 km/h (163.4 mph) at the 2012 Busan Open Challenger in South Korea. This is recognized as the fastest serve in the Guinness World Records. However, this speed is not officially recognized by the ATP because the tournament was not an ATP event. The fastest ATP Tour-recognized serve is held by John Isner at 253 km/h (157.2 mph). Among women, the record is held by Georgina Garcia Perez at 220 km/h (136.7 mph).
How far does a tennis ball travel during a serve?
This calculator uses 18 meters as the standard service distance, which represents the approximate total distance from the server (standing behind the baseline) to the returner's baseline on the opposite side of the court. The ITF rules specify that the service box starts at the net and extends 6.40 meters toward the baseline on the returner's side. The total court length is 23.77 meters, but the serve must clear the net from a position behind the baseline, making the effective ball flight distance approximately 17 to 20 meters depending on the angle and server's position.
Official sources
- ITF Rules of Tennis: ITF Rules and Regulations.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. General information only.