CMJ Power Calculator (Sayers, Harman & Lewis)
Estimate peak and average power of a countermovement jump from jump height and body mass using the Sayers, Harman and Lewis regression equations from the sports-science literature.
Results
- Peak power
- 3,771 W
- Sayers peak
- Relative power
- 50.3 W/kg
- Power ÷ body mass — the most useful number when comparing athletes of different sizes
- Peak-power spread
- 3,771 - 6,998 W
- Lowest to highest across available peak-power equations
- Average-power spread
- 1,030 - 1,180 W
- Lowest to highest across available average-power equations
All equation estimates
| Equation | Power | Relative power |
|---|---|---|
| Sayers et al. (1999) — peak power | 3,771 W | 50.3 W/kg |
| Harman et al. (1991) — peak power | 6,998 W | 93.3 W/kg |
| Harman et al. (1991) — average power | 1,180 W | 15.7 W/kg |
| Lewis — average power | 1,030 W | 13.7 W/kg |
How it works & limitations
What these equations estimate
Sayers (1999) and Harman (1991) predict peak power; Lewis predicts average power; Johnson & Bahamonde (1996) predicts peak power and additionally uses body height. All four are regression equations derived from vertical-jump testing and cross-validated against force plates or a force platform reference. Individual error is commonly around 5-10%.
Which equation to use
Sayers was derived from squat-jump data and is often applied to the CMJ; Harman's equations come from vertical-jump testing and are widely used in field testing; Lewis is an older average-power estimate that tends to be the least precise for fast jumps. For consistent tracking, pick one equation and always use the same jump type, measurement method and equation.
Relative power (W/kg)
Dividing power by body mass normalises for body size, which matters because heavier athletes generally produce more absolute power. W/kg is the value coaches usually compare within a squad or across testing sessions.
Sources
Last updated 2026-08-13
- Sayers, S. P., Harackiewicz, D. V., Harman, E. A., Frykman, P. N., & Rosenstein, M. T. (1999). Cross-validation of three jump power equations. Medicine & Science in Sports & Exercise, 31(4), 572-577.
- Harman, E. A., Rosenstein, M. T., Frykman, P. N., Rosenstein, R. M., & Kraemer, W. J. (1991). Estimation of human power output from vertical jump. Journal of Applied Sport Science Research, 5(3), 116-120.
- Johnson, D. L., & Bahamonde, R. (1996). Power output estimate in university athletes. Journal of Strength and Conditioning Research, 10(3), 161-166.
Regression estimates, not direct force-plate measurements. Use one equation consistently and interpret changes of less than about 5-10% with caution.
Frequently asked questions
Which jump-power equation should I use?
The Sayers and Harman equations estimate peak power and were cross-validated on vertical-jump data; the Lewis equation estimates average power. They agree broadly but can differ by 10% or more for individuals, so pick one equation and stay consistent when tracking changes.
How accurate are these formulas compared with a force plate?
These regressions use only jump height and body mass, so they explain a large share of the variance in force-plate power but cannot match direct measurement for individuals. Treat results as estimates and use the same method every time.