Mouse: Sensor, DPI and polling rate

In short: An optical mouse films the surface and calculates the movement from it; DPI says how far the pointer moves per centimetre of movement.

In more detail: Modern mice have a small camera sensor that takes images of the surface thousands of times per second and calculates displacements. The data goes to the computer by cable or radio. Some values on the packaging matter more than others.

In Depth

Sensor types

Optical sensors use an LED or an infrared laser. Today optical sensors with high accuracy dominate; laser sensors also work on glass but can “scratch” (unclean movements). On glass surfaces or very smooth bases special sensors help.

DPI (CPI)

DPI (dots per inch) states how many counting steps the sensor reports per inch of movement. At 800 DPI the mouse sends 800 steps per 2.54 cm. More DPI means a faster pointer for the same hand movement. Numbers such as “25,000 DPI” are marketing: for everyday use 800 to 1600 suffice, for high-resolution monitors more. What matters is adjustability and that pointer acceleration can be switched off in the operating system.

Polling rate

It states how often the mouse sends its position to the computer. Standard is 125 Hz (every 8 ms); gaming mice reach 1000 Hz (1 ms) or more (4000 or 8000 Hz). Higher rates feel smoother, need more processor time and, for wireless mice, more battery.

Other features

• Connection: cable (no delay, no battery), 2.4 GHz radio with USB receiver (low latency) or Bluetooth (convenient, somewhat slower).
• Weight and shape (right/left-handed, hand size, grip style).
• Buttons: side buttons, scroll wheel with tilt or free spin.
• Battery.
• Software for button mapping and macros. In everyday use ergonomics matter more than peak values.

See also: Mouse, Working with the mouse, Connecting Bluetooth