Convert between frames per second and frame time in milliseconds.
| FPS | Frame time | Where you see it |
|---|
Frame rate and frame time describe the same thing from opposite ends: how many frames arrive each second, and how long each one takes. Frame time is the more useful of the two when you are chasing stutter, because a run of good average FPS can still contain single frames that took far too long.
The maths: frame time in milliseconds = 1000 ÷ frames per second, and the reverse is the same sum the other way round. 60 FPS is 16.67 ms per frame; 144 FPS is 6.94 ms.
Because an average hides the spikes. A game running at an average of 90 FPS that occasionally takes 40 ms to deliver a frame feels like it stutters, even though the average looks healthy. Frame time shows you the individual bad frames that the average smooths away.
Match your monitor first. A 60 Hz screen cannot display more than 60 frames a second, so frames beyond that are being discarded. On a 144 Hz or 165 Hz screen, aim for a frame rate you can hold steadily rather than a high one that keeps dipping — consistency feels better than a higher but unstable number.
It is the frame rate of your worst 1% of frames — in effect, how bad the rough patches get. A game showing 120 FPS average with a 40 FPS 1% low will feel noticeably less smooth than one at 90 average with an 80 FPS 1% low.
Up to a point. Beyond your monitor's refresh rate the extra frames are not displayed, though they can still slightly reduce input lag. A stable frame rate that matches your screen beats a higher one that fluctuates.
Because 1000 divided by 30 does not come out even. The recurring decimal is why 30 and 60 FPS caps are not perfectly even numbers of milliseconds.
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