About Girth to Diameter

girthtodiameter.com has a single purpose. You type the distance around something round, called its girth, and it tells you the distance straight across, called the diameter. It also works the other way round. The same simple rule fits anything round, from a pipe or a tree trunk to a wrist, a ring or a part of the body.

Where the numbers come from

Every answer rests on one well-known number, pi, which is about 3.14. The distance around any circle is pi times the distance across it, and the site does that sum for you. It also switches between inches and centimetres, using the fixed rule that one inch is 2.54 centimetres.

All the working out happens on your own phone or computer, so nothing you type is sent to us or to anyone else.

The average sizes on the home page come from published research in which health professionals measured the men in each study, and each figure links to its source. These averages describe large groups, so your own size can be quite different and still be normal.

The company

Circumference Tools Ltd runs the site.

Contact us

We are glad to hear from you. Questions, corrections to a source link and requests about your data can all go to [email protected].