DPI stands for dots per inch. The DPI rating of your mouse determines how far you can send your cursor across your computer screen when you move the mouse one inch. The dots are the equivalent of screen pixels. A DPI rating of 400 means you can direct your cursor across 400 pixels when you move the mouse by an inch. A mouse with a high DPI rating is therefore more sensitive than one with a low DPI rating. This sensitivity can be important for gaming and the creation of on-screen graphics.
Turn your mouse over. The flat bottom of your mouse usually has information on it. This may include the DPI. If you have a mouse with "on-the-fly" settings, the information may show a range of DPIs. You can adjust the DPI to suit your screen and your computing needs. You can make an "on-the-fly" adjustment with a button on the side of the mouse. Please note that manufacturers are not obliged to show the DPI rating on a mouse.
Go to the manufacturer's website if you cannot find the DPI on the mouse itself. Search for your mouse model and check the specifications. Be aware that some manufacturers give full DPI details on their websites while others do not.
Load the software that came with your mouse. If the software is not in the form of a CD, you may be able to download it from the manufacturer's website. Again, look for the specifications of the mouse. These should show the DPI. You may also be able to use the software to adjust the DPI of your mouse.
Search for the make and model of your mouse online. A website that sells your mouse may show specifications that include the DPI. Some forums also discuss mouse DPIs.
The pixel quality of your computer screen also affects the distance you can send your cursor when you move your mouse. A mouse with a high DPI rating is only effective when you have a screen with a large number of pixels.