Release the mouse button to stop recording the movement.The goal is to move your mouse physically the target distance and see where the red crosshair ends up. The goal is NOT to try to move the red crosshair on top of the blue one, this is just an indicator of where 0% deviation is.Move your mouse the target distance as mapped out on the piece of paper (or however you prefer to measure it).Click the red crosshair, and hold the mouse button down.You do not need to enter this if it is unknown, but it is necessary for the accuracy calculation. Enter the current DPI setting, if known.Enter the target distance for how far you are moving your mouse.You need to accurately measure how far you move your mouse, so do something like drawing inch/cm lines on a piece of paper and use it as a mousepad.The target count and actually moved counts are also shown.The actual DPI is shown with an accuracy of two decimals.You can measure the X-axis both ways, select X- to measure from right to left.

It can also be used to find out what your DPI actually is if you don't have a setting for it in your mouse driver. With this tool you can measure the real DPI of your mouse, and calculate the sensor accuracy.

Photo of a mouse