How high over the net should you hit in tennis

Draw your margin. Aim at the window, not the line.

Key facts

1
The net is 0.914 m high at the centre and the court is 23.77 m long, so every ball threads a window between the two.
2
In a ball-flight model at 25 m/s, a flat ball has a window of launch angles 6.9° wide, and 3,200 rpm of topspin widens it to 11.3°.
Ball-flight model, illustrative
3
In the same model at 30 m/s, the window shrinks to 3.9° flat and 8.0° with 3,200 rpm.
Ball-flight model, illustrative
4
Topspin gives about 2.5 times the vertical margin of slice.
Brody, Cross & Lindsey
5
One percent more racquet speed sends the ball about 18 in deeper, and one degree more launch angle about 6 ft longer.

Why it works

Two things end a shot: the net and the baseline. Gravity and drag pull the ball toward the first. Speed pushes it toward the second. Spin is the only ingredient that pulls the ball down without slowing it, so it's the only one that widens the window at a given speed. Aim high, add spin, and the air brings the ball back inside.

Speed narrows the window, spin widens it, and height moves it. Drag matters more than it feels: at 30 m/s, drag on a ball is about 0.93 N against a weight of 0.56 N.

Contact height flips the geometry. From about 1 m on a groundstroke the window sits above the net. From about 2.8 m on a tall player's serve it points down into the box, and it's narrow: in a ball-flight model at 40 m/s, 1.8° flat and 3.8° with 2,500 rpm.

The line to say on court
“Aim at the window, not the line.”

Drill: The slot

15 min · alone or with a partner

Tie two ropes above the net, at 1 m and 2 m. Hit ten forehands through the slot between them, any depth.
Hit ten more through the slot that also land past the service line.
Rally ten balls with a partner, through the slot and past the service line. Count them.

Number to beat7 of 10 through the slot and past the service line

More drills like this: practise alone

Faults and fixes

Aiming at the line

You're aiming at an edge of the window.

FixAim at the middle of the band, two metres inside the line.

Skimming the tape

The flat window is only a few degrees wide.

FixRaise the target and add spin.

Height without spin

The ball floats long.

FixSteepen the swing path, not the aim.

Trusting feel

Margin is geometry, not a feeling.

FixMeasure your clearance with a rope once a week.

Questions players ask

Why do my shots keep going long?

Too much speed or launch angle for the spin you're using. Aiming lower squeezes you into the narrow flat window, and swinging slower costs pace. Adding topspin widens the window at the same speed.

Does topspin help keep the ball in?

Yes. It pulls the ball down without slowing it, so you can clear the net by more and still land inside the baseline.

Does hitting harder make it harder to keep the ball in?

Yes. Speed narrows the window: in a ball-flight model a flat ball's window is 6.9° at 25 m/s and 3.9° at 30 m/s.

Why is the serve so hard to get in?

Contact at about 2.8 m points the window down into the box, and it's narrow. In a ball-flight model at 40 m/s it's 1.8° flat and 3.8° with 2,500 rpm.

What this doesn't cover

The window figures come from a ball-flight model, not measurement. Drag and lift change with ball wear and speed, while the model holds drag constant and caps lift. The serve window ignores the bounce and the sidelines.

Sources

Mehta, "The aerodynamics of a tennis ball," Sports Engineering (2001)
Tennis Warehouse University, "Tennis Ball Trajectories"
Cross & Lindsey (2013): tennis ball free-flight research
Brody, Cross & Lindsey, The Physics and Technology of Tennis
Hoong, "Exploring Tennis Ball Trajectories"

StrikeHow to hit topspin in tennisTo hit topspin, swing low to high so the racquet brushes up the back of the ball with a slightly closed face, instead of driving through it. The path makes the spin, not a wrist roll: the ball has left the strings before a rolled wrist closes the face. Polyester strings add a bonus on top of whatever spin your path makes.StrikeHow topspin works: the Magnus effect in tennisTopspin works through the Magnus effect: a spinning ball drags air around with it, and the pressure difference pushes the ball at right angles to its spin axis. With topspin that push points down, so the ball dives. At heavy pro topspin the push is about 0.5 N, close to the ball's own 0.56 N weight. That lets you aim high, swing hard and still land it.StrikeWhen to hit flat and when to hit topspin in tennisHit flat when the ball is short and low and you're inside the baseline. Hit topspin when you're deep and the ball is high. One racquet-head speed buys either a flat drive or a heavy ball, never both. Tilt the swing path upward and you trade forward speed for spin, which gives you more margin but lands shorter.Play the pointWhat is percentage tennis and how do you play itPercentage tennis means choosing targets and shots so the point ends on your opponent's error more often than on yours. It isn't pushing. It's aggressive with margin: aim through the net window, land past the service line, and go to the bigger half of the court and the weaker wing. About two in three points end on an error.