A Regulation Ping-Pong Ball Is 40 mm in Diameter
A regulation ping-pong ball is 40 mm (4 cm or 1.57 inches) across and weighs 2.7 g. Here is what the 40+ marking means.
A regulation ping-pong ball is 40 millimetres in diameter. That is 4 centimetres or approximately 1.57 inches across.
The ITTF’s 2026 rules specify a spherical 40 mm ball weighing 2.7 g. They also require the ball to be made of plastic, finished matt and coloured white or orange.
| Measurement | Regulation specification |
|---|---|
| Diameter | 40 mm |
| Diameter in centimetres | 4 cm |
| Diameter in inches | 1.57 in |
| Weight | 2.7 g |
| Shape | Spherical |
The inch figure is a conversion rather than a separate standard: 40 ÷ 25.4 = 1.5748 inches, conventionally rounded to 1.57 inches.
What does “40+” on a ball mean?
“40+” does not mean that table tennis uses a different nominal diameter. It identifies the plastic-ball generation rather than the former celluloid ball.
The ITTF’s 2014 technical leaflet required non-celluloid balls and their packaging to carry “40+”. That leaflet allowed an individual non-celluloid ball to have a measured minimum diameter of 40.00 mm and maximum diameter of 40.60 mm while the rule still described the ball as 40 mm. This is why a 40+ ball can measure slightly more than 40.00 mm without “40+” being a new regulation diameter. Those figures describe the approval tolerances in that dated technical document, not a claim that every ball measures 40.60 mm. (ITTF Technical Leaflet T3, 2014)
Was the ball always 40 mm?
No. The official ball used to be 38 mm. The ITTF says the 38 mm ball was replaced by the 40 mm ball in October 2000, after the Sydney Olympics; it also records the move from celluloid to polymer balls from 2015. (ITTF history of the sport)
For current play, the practical buying shorthand is therefore 40+ plastic ball. For the underlying regulation measurement, the answer remains 40 mm. If you are checking tournament equipment rather than answering the measurement question, look for the relevant competition’s approved-ball requirements as well as the printed size.