Ideal depth for CPR is no deeper than 5.5 cm or 2 inches, in adult people.
If you go any deeper, you can damage the internal organs.
Any lower, you may not pump the blood effectively through the body.
It doesn't sound a lot when we say that it takes only 2 inches. But it takes a lot of force as well to compress a human chest . by two inches. About 60 pounds of force. It is easy to over-deliver especially if you have a lot of strength. It's important to be delicate especially if you don't have experience in pushing on a body.
