DPI in simple terms
DPI stands for dots per inch. In mouse discussions it is used to describe how many sensor counts are associated with one inch of physical movement. Higher configured DPI generally means the operating system receives more counts for the same physical movement.
For example, moving a mouse one inch at 800 DPI produces about twice as many counts as one inch at 400 DPI, assuming the rest of the input path is comparable.
DPI does not mean accuracy
A higher DPI setting is not automatically more accurate. Sensor quality, implementation, tracking behavior, surface compatibility, firmware and your own control all matter. A high DPI can also make a setup feel too fast if game sensitivity is not adjusted.
DPI, CPI and eDPI
DPI is the common marketing term; CPI, counts per inch, is often a more technically precise description of sensor counts. In gaming, eDPI commonly means mouse DPI multiplied by in-game sensitivity. eDPI is useful for comparing setups within a game, while cm/360 expresses the same idea in physical movement terms.
Why two players can use the same DPI
Two players can both use 800 DPI and have very different sensitivity because their in-game sensitivity settings differ. Conversely, 400 DPI and 800 DPI can be paired with different game sensitivities to produce similar effective sensitivity.
How to choose a practical DPI
Choose a value that works with your mouse, pad, game and preferred control range. Avoid treating an internet-wide “best DPI” number as a rule. Record the full setup and compare physical movement or eDPI when changing it.
Check your current DPI
If you do not know your mouse setting, check the manufacturer's utility first. For a browser-based independent estimate, use the Mouse DPI Analyzer and repeat several trials.