DPI and CPI explained
DPI is the most quoted mouse specification and the least consequential. Once your eDPI is fixed, changing DPI changes nothing about your aim. What it does change is subtler, and worth knowing about precisely because it is not what the marketing says.
What the number measures
A mouse sensor is a small camera taking thousands of pictures of your mousepad every second and comparing consecutive frames to work out how far the surface moved. DPI is the resolution of that measurement: how many discrete steps, or counts, the sensor reports for every inch of physical travel.
At 800 DPI, one count is 1/800th of an inch, or about 32 micrometres. At 3200 DPI, one count is about 8 micrometres. Both are far finer than anything your hand does on purpose: deliberate human movement resolution at the fingertip is on the order of a tenth of a millimetre at best, which is roughly three counts at 800 DPI.
Why it does not affect your aim
The game multiplies incoming counts by your sensitivity. Double the DPI and halve the sensitivity, and the product is unchanged, so the rotation per unit of physical movement is unchanged. Your aim is the product, not either factor.
| DPI | Sensitivity | eDPI | cm/360 | Counts per 360 |
|---|---|---|---|---|
| 400 | 2.00 | 800 | 51.9 | 8182 |
| 800 | 1.00 | 800 | 51.9 | 16364 |
| 1600 | 0.50 | 800 | 51.9 | 32727 |
| 3200 | 0.25 | 800 | 51.9 | 65455 |
The only column that changes is the last one. Higher DPI means the same physical turn is described by more counts, which is a finer description of the same movement. That finer description is only useful if something downstream can use it, and your hand cannot.
Where DPI does matter
At the very bottom of the range
Below about 400 DPI, count granularity starts to approach the scale of deliberate small movements. A 400 DPI mouse reports one count per 63 micrometres; a very fine correction may span only a handful of counts, and the quantisation becomes visible as a slight stepping in slow tracking. This is a real effect, and it is the one legitimate argument for not going lower.
At the very top, in combination with low sensitivity
Very high DPI paired with a very low in-game sensitivity means the engine is dividing a large count stream by a small number. Some engines accumulate the remainder correctly; others round per frame, which produces small inconsistencies in slow movements. It is not a large effect, but it is why 3200 DPI at 0.15 sensitivity is a worse configuration than 800 at 0.6 for the same aim.
On the desktop
This is the genuinely practical one. 400 DPI is unpleasant outside a game: you will be dragging your mouse across the whole pad to cross a 4K desktop. 1600 is comfortable on a large display. If you want a high desktop DPI, use it, and drop your in-game sensitivity to compensate.
With 8000 Hz polling
High DPI at 8 kHz produces a lot of USB interrupt traffic. On systems that are already CPU constrained, this can measurably cost frame pacing, which is worth more than the report timing you gained. See polling rate.
The practical recommendation
Use 800 DPI. It is comfortably above the granularity floor, comfortably below the range where engine rounding and interrupt load become considerations, available on every mouse ever made, and it makes eDPI arithmetic trivial. If you want a faster desktop pointer, use 1600 and halve your in-game value. There is no third consideration.
Native resolution, interpolation and why it stopped mattering
Older optical sensors had a native resolution, and higher settings were produced by interpolating between real measurements. Interpolation invents data, and invented data in a position sensor shows up as smoothing (movement lagging your hand) or jitter (movement your hand did not make). This is where the folklore about low DPI being "more accurate" comes from, and at the time it was correct.
Modern flagship sensors have native resolutions in the tens of thousands of counts per inch and do not interpolate anywhere in the range you would plausibly use. The concern is genuinely obsolete on any mouse released in the last decade with a mainstream sensor. See mouse sensors for what the current parts actually do.
Related reading
- eDPI, the number that DPI is only half of.
- Mouse sensors: what a 30K sensor is and why the number is marketing.
- Polling rate, the specification people confuse with DPI most often.
Frequently asked questions
What is the difference between DPI and CPI?
Nothing, for a mouse. CPI (counts per inch) is the technically correct term, because a mouse sensor reports counts rather than printing dots. DPI was borrowed from printing and stuck. Some manufacturers use CPI to signal they know the difference; the number means the same thing.
Does higher DPI make my mouse more accurate?
Not in any way you will notice above roughly 800. Higher DPI means finer reporting granularity, so the smallest movement the sensor can report corresponds to a smaller physical distance. Above about 800 that granularity is already far finer than your hand's ability to move deliberately, so the extra resolution goes unused.
Why do so many players use 400 or 800 DPI?
History. Early optical sensors genuinely degraded above their native resolution: they interpolated, which introduced smoothing and jitter. 400 was safely native on almost everything, so the competitive scene standardised on it and the habit outlasted the hardware limitation. Modern flagship sensors have native resolution far above anything you will use.
Is there a downside to very high DPI?
Two small ones. Very high DPI plus a very low in-game sensitivity means the game divides down a large stream of counts, and some engines quantise that division in ways that produce slightly uneven small movements. And at 8000 Hz polling, high DPI generates a lot of USB traffic and CPU interrupts, which can cost frame pacing on weaker systems.
Is my mouse's DPI actually the number in the software?
Often not exactly. Sensor DPI steps are calibrated approximations, and a mouse set to 800 may actually be reporting 790 or 815. The error is small and constant, so it does not affect consistency, but it does mean a calculated cm/360 can be a percent or two off a measured one. Measure if you care about the exact figure.