# Table Tennis ball Dimensions

Top tips to help you choose your ideal table tennis ball.

Part two - What criteria do ITTF approved 40mm balls have to meet.

| Part Two - Approved 40mm TT balls

In part one we looked at the different types of table tennis balls and what the rules say about them.

We also looked at the two most recent major changes made to the ball which affected the size of the ball and the material used to make them.

So let's now take a look at the tests which are carried out on **table tennis balls** in order to meet the criteria set by the ITTF and then view a list of the balls which appear on the .

OK, let's get started...

^ ^

Tests are first carried out for...

### General Appearance

The ball must be white or orange, and matt, and must appear to be uniform and only have one seam.

The stamp on the ball may cover an area no greater than 280mm2 and be printed in one or two colours, but the same colour or combination must be used for all balls of the same brand and the wording must comply with ITTF regulations.

The balls must be packaged appropriately, e.g. in paper or plastic boxes or in a blister pack. And the wording used on this package has to contain either "40" or "40mm" for celluloid balls or "40+" for non-celluloid balls.

The packaging of the balls must also contain a date or a date code and must comply with the ITTF regulations.

And then there are tests which are carried out on a batch of 24 balls which include the following...

### Weight

Although the official rules state that the ball shall be 2.7g, any weight between 2.67g and 2.77g is acceptable for any one ball in the test batch.

No more than one ball out of the 24 tested may be outside this range and the sample mean must be between 2.69g and 2.76g.

### Size

For celluloid balls the minimum diameter of every ball must be at least 39.50mm, and its maximum diameter must not exceed 40.50mm.

The sample mean average diameter, i.e. the mean of the average of the maximum and minimum diameters for each ball, must be in the range 39.60-40.40mm

For non-celluloid balls the minimum diameter of every ball must be at least 40.00mm and its maximum diameter must not exceed 40.60mm.

The sample mean average diameter, i.e. the mean of the average of the maximum and minimum diameters for each ball, must be in the range 40.00-40.50mm.

### Sphericity

The sphericity of a ball - or more correctly the lack of sphericity - is the absolute difference between its minimum and maximum diameters.

For celluloid balls the sphericity of any ball must be less than 0.35mm, and the sample mean sphericity must be less than 0.25mm.

For non-celluloid balls the sphericity of any ball must be less than 0.25mm, and the sample mean sphericity must be less than 0.20mm.

### Bounce

All 24 balls must rebound to a height of not less than 240mm or more than 260mm when dropped from a height of 305mm on to a standard steel block.

### Veer

Veer is a measure of the total sphericity of the ball.

It's measured by rolling the ball down a slight incline onto a horizontal surface, and measuring the distance by which it deviates from a straight line as it rolls across the surface.

The incline is 100mm long at 14 degrees to the horizontal, and on a table that is 100cm long this gives a rolling time of about 3 seconds.

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