1% low
The 1% low is the frame rate of the slowest 1% of frames, capturing the stutters that an average frame rate hides entirely.
Also known as 1% low fps, 99th percentile frame time, 0.1% low
Measured by SystemCheck
Part of the four-stage run: a 60-second sustained CPU load reporting throughput, decay and consistency; a memory stage reporting bandwidth and latency; a calibrated GPU raster load reporting frame time, pacing and decay; and a path tracer reporting samples per second. The paragraphs below say which metric carries this term.
Sort every frame time in a run, take the slowest one percent, and express it as a frame rate. It is the same data as the 99th-percentile frame time, expressed the way gamers read it. The 0.1% low goes further into the tail and captures rarer, more severe hitches.
The gap between average and 1% low is the practical smoothness metric. A machine averaging 120 fps with a 100 fps 1% low feels excellent; one averaging 120 fps with a 45 fps 1% low feels broken despite the identical average. When someone says a game "stutters" on a fast PC, this gap is almost always what they are describing.
Percentile thinking is why SystemCheck scores from the distribution of frame times rather than the mean. The consistency figure in a SystemCheck report is built on the same idea: how bad are the bad frames, not how good is the typical one.
Related terms