Velocity loss calculator: what a slower rep means

By Konshu · 23 October 2026 · 5 min read

Velocity loss is the percentage drop from a reference rep speed to a later rep in the same set. Enter both speeds below to calculate it. A change from 0.70 to 0.56 m/s equals 20% velocity loss.

Velocity loss compares a later rep with a reference rep in the same set. If the first rep moves at 0.70 m/s and a later one moves at 0.56 m/s, the drop is 20%. It describes the speed change. It does not, by itself, tell you exactly how many reps remain or whether the set should end.

The calculation

For the example above, (0.70 − 0.56) ÷ 0.70 × 100 = 20%. Both readings must come from the same set and use the same velocity measure. A later rep faster than the reference produces a negative result; that is a speed gain, not velocity loss.

Some systems use the fastest rep as the reference instead of the first rep. That choice changes the answer when your first rep is slow. Always check which definition your device uses before comparing percentages.

Try the calculator

Enter two velocities from the same set, using the same speed metric and device. The graph updates as you type.

Does 20% mean “stop”?

It depends on what you are training for, which exercise you chose and what the rest of the program looks like. A 2023 dose–response meta-analysis reported that 20–30% loss may be helpful for maximal strength development in the studied trained men, while lower loss appeared more efficient per repetition. The authors also identified important limits: no female participants in the included studies, sparse data for some thresholds, and insufficient data to separate squat from bench press effects.

That is a research result for a defined group, not a universal target for every lifter. If you are trying to keep every rep fast for power, you may use a different approach from someone accumulating harder strength work. The same percentage can represent a different experience at a different load.

Use the number well

1. Compare reps from one exercise and one set, measured in the same way.
2. Review the shape of several sets, not one stray reading.
3. Record the load, reps and how hard the set felt beside the speed data.
4. Use a planned stopping rule only when it fits your training goal and measurement setup.

The useful question is not “Is this percentage good?” It is “What changed, and what decision does that support?” For the broader picture, read the VBT guide or compare speed with rep count.

← All articles