eDPI and cm/360 Explained: DPI, Sensitivity and Game Conversion

DPI, sensitivity, eDPI and cm/360 all describe the same thing from different angles: how far your hand has to move to turn your view. Only one of them, cm/360, is a physical distance you can check with a ruler. None of them changes your reaction time test score directly, but they shape everything that happens after you react.

DPI is the mouse, sensitivity is the game

DPI (or CPI) is how many counts the mouse sensor reports per inch of movement. It's a mouse setting, usually changed in the maker's software. The number you set is nominal, and the physical distance a sensor actually tracks per count can differ from it.

In-game sensitivity is the game's multiplier. Under the hood, a game turns each count into some angle of rotation. The yaw coefficient is that angle in degrees per count at sensitivity 1. The coefficient differs between games and sometimes between versions or aiming modes.

If a game doesn't use raw input, your operating system's pointer speed and acceleration can also change the result. Everything below assumes a linear relationship: each count turns the view by the same angle, however fast you move.

eDPI: a shortcut that only works inside one game

eDPI (effective DPI) is DPI multiplied by in-game sensitivity:

Within one game, these three setups turn the view the same distance per centimetre of hand movement. That makes eDPI handy for comparing settings with teammates who play the same game.

It breaks down across games. A game with a larger yaw coefficient turns further per count, so the same eDPI produces a faster turn. Equal eDPI in two different games can give very different turn distances.

cm/360: a distance you can measure

cm/360 is how many centimetres of mouse travel make one full horizontal turn:

cm/360 = (360 × 2.54) / (DPI × sensitivity × yaw)

The denominator is degrees of turn per inch of travel. Dividing 360 degrees by it gives inches per turn, and multiplying by 2.54 converts to centimetres. That conversion is exact: NIST defines one inch as exactly 25.4 mm.

Here is an arithmetic example with an invented yaw of 0.05, not a real game value. At 1000 DPI and sensitivity 2, you get 100 degrees per inch, so a full turn takes 3.6 inches, or 9.144 cm. With the same sensitivity and yaw, changing DPI changes the distance in proportion:

The WiredReflex cm/360 calculator does this calculation from the three numbers you enter: DPI, sensitivity and yaw coefficient. It deliberately has no game presets. If you don't know the documented yaw for your game version and aiming mode, it won't guess. It doesn't detect your DPI or measure your movement either. The page includes a ruler procedure for checking the result in game.

Converting sensitivity between games

To keep the same cm/360 in a new game, keep DPI × sensitivity × yaw constant. With the same DPI:

new sensitivity = old sensitivity × (old yaw / new yaw)

If you also change DPI:

new sensitivity = old sensitivity × (old DPI × old yaw) / (new DPI × new yaw)

For example, with invented coefficients: moving from a game with yaw 0.05 to one with yaw 0.02 at the same DPI, sensitivity 2 becomes 2 × (0.05 / 0.02) = 5. Both give 0.1 degrees per count.

Matching cm/360 matches hip-fire turn distance, and nothing more:

• Scopes and ADS often apply their own multipliers, so they need a separate conversion.
• Field of view changes how a turn looks on screen. Equal cm/360 doesn't mean equal on-screen motion or the same feel for small adjustments.
• Coefficients change. Use the game's current documentation or source, and verify with a ruler.

Low vs high sensitivity

Pointing research treats sensitivity as control-display gain: how far the cursor or view moves for a given hand movement. Casiez and colleagues (2008) studied mouse gain and described a usable range bounded by speed and accuracy limits, not one perfect value. Gaming sensitivity runs into the same two limits:

Two practical points follow from the arithmetic:

• The per-count step is sensitivity × yaw. 400 DPI at sensitivity 4 and 1600 DPI at sensitivity 1 give the same cm/360, but the second setup turns a quarter as far per count, so each step is finer. How well a sensor behaves at higher DPI depends on the model.
• DPI also affects report rate. A mouse only sends motion reports when it has new counts. At low DPI and slow hand speeds it may not fill a high polling rate. See mouse polling rate explained.

There's no validated "pro range" to copy. Pick a setting you can repeat, change it in small steps, and give yourself several sessions before judging a change.

Sensitivity and reaction time

Sensitivity doesn't change how fast you detect a cue. It changes what happens after: the flick, the stop and the correction. That's why reaction time vs aim speed treats them as separate skills, and why aim throughput is measured separately from simple reaction time.

Browser aim tasks have one more limit. MDN notes that movementX values may be in physical, logical or CSS pixels depending on the browser and operating system, so a web page can't turn mouse movement into calibrated centimetres. Browser aim scores are same-setup relative.

Sources & context

The unit conversion follows the NIST length reference (1 inch = 25.4 mm exactly). The gain tradeoff comes from Casiez, Vogel, Balakrishnan and Cockburn, The impact of control-display gain on user performance in pointing tasks (Human-Computer Interaction, 2008), a desktop pointing study rather than an FPS study, so treat it as the model behind the tradeoff, not a prescription for game settings. Browser movement units are described in MDN's movementX reference. All yaw values in this guide are invented for arithmetic. See how we measure for the limits of browser-observed timing.