How Big Is a Ping-Pong Ball? The 40 mm Answer
A regulation ping-pong ball is 40 mm (4 cm or 1.57 inches) in diameter and weighs 2.7 g. See how to measure it and use it in serve practice.
A regulation ping-pong ball is 40 mm in diameter. That equals:
- 4 cm
- 1.57 inches
- 20 mm radius
- About 12.57 cm (4.95 inches) around its circumference
Because the ball is spherical, its width and height are both 40 mm. The 2026 Laws of Table Tennis also specify a weight of 2.7 g and require the ball to be made of plastic, with a matt white or orange finish. The ITTF identifies its official 2026 statutes as applicable from January 1 through December 31, 2026 on the federation’s document page.
Ping-pong ball measurements at a glance
| Measurement | Regulation size |
|---|---|
| Diameter | 40 mm / 4 cm / 1.57 in |
| Radius | 20 mm / 2 cm / 0.79 in |
| Circumference | About 125.7 mm / 12.57 cm / 4.95 in |
| Weight | 2.7 g |
The diameter is the straight-line distance through the center of the ball. To check one with a ruler, place the ball between two square, parallel objects and measure the gap between them. Measuring across the top by eye is less reliable, while wrapping a tape around the curved surface measures circumference rather than diameter.
Use the ball as a quick serve-toss reference
The ball’s size gives you a convenient visual check when rehearsing your serve. The laws require the ball to rise at least 16 cm after leaving the hand, which is exactly four 40 mm ball diameters. For the complete requirements around the toss, visibility and contact, use this legal serve checklist.
Five-minute solo check
Setup: No partner or robot is needed. Stand at the table with four balls and your racket. Stack the balls beside a wall or net post to see what 16 cm looks like, then remove them before serving.
Action:
- Make five shadow tosses, aiming for the bottom of the ball to rise at least the height of the four-ball stack.
- Serve 10 balls while keeping the toss near vertical and contacting the ball as it falls.
- Alternate five backspin serves with five disguised no-spin serves. If those are still new, work through your first three spin serves.
Checkpoint: Film from the side at table height. Pause each repetition at the top of the toss and compare the rise with your 16 cm reference. Count a repetition only when the toss clears that reference without drifting sharply sideways.