Why it is the number that transfers
DPI and in-game sens are inputs. cm/360 is the output: how far your hand actually moves. Two players with the same cm/360 make identical arm and wrist movements for the same turn, whatever their mice are set to, and whichever game they are in.
Read it the right way round. A higher cm/360 is a lower sensitivity, because it takes more mouse travel to get around. 60 cm/360 is slow and precise, 20 cm/360 is fast and twitchy.
The formula
Yaw is the number of degrees the game turns per mouse count at sensitivity 1. It is a fixed constant per game: 0.022 in CS2 and Apex, 0.07 in Valorant, 0.0066 in Overwatch 2. The 2.54 converts inches to centimeters.
Example: CS2 at 800 DPI and 1.1 sens. 0.022 × 1.1 × 800 is 19.36 degrees per inch, 360 divided by that is 18.6 inches, and 18.6 × 2.54 is 47.2 cm per 360.
You do not have to remember any of this. The eDPI calculator shows your cm/360 for the game you pick, and the converter uses it to carry a sens into another game.
Measure it with a ruler
No software needed. Put your mouse at one edge of the pad, note the position, and drag it in a straight line until your view has turned exactly once, with a landmark ending back where it started. Read the distance off a ruler. That is your cm/360.
Do it two or three times and average. If your measured number does not match the formula, something between the mouse and the game is scaling your input, usually Windows pointer speed or mouse acceleration.
Typical values
Converted from the pro eDPI ranges, Valorant and CS2 pros both land somewhere between about 36 and 65 cm per 360. Apex and Overwatch 2 pros run faster, mostly between about 25 and 50 cm. Hero shooters and arena games trend faster than tactical ones because targets move more and headshots decide less.
None of that is a target for you. Pick a cm/360 you can control, keep it for months, and let your hand learn it. Hopping between sensitivities is one of the fastest ways to stall, and it is covered in 7 aim mistakes that keep you hardstuck.