Accurately measured, the coffee tamper’s inner diameter should be smaller than the inner diameter of the basket. So you can equitably smaller the ground espresso. The best technique to recognize the right alter size is to quantify the specific inside size of your basket utilizing mechanical engineer calipers. If you don’t approach a bunch of calipers, you can likewise utilize a steel estimating tape with 1/32″ divisions and an extremely cautious eye and consistent hand to take the estimation and afterward convert it to millimeters.

And the easiest way to choose the right size tamper is refer here below table, according to the brand to choose right size.

Automatic Coffee Tamper Size Reference Chart