RSI Calculator (Reactive Strength Index)
Calculate reactive strength index from jump height and ground contact time, with drop-jump interpretation ranges and the testing notes you need for valid results.
Results
- Reactive strength index
- 1.5 m/s
- Jump height (m) ÷ ground contact time (s)
- Athlete percentile
- ~P20
- P10-P25 · combined-athlete RSI norms
RSI norms — combined athletes (Plyomat, per-athlete bests)
| Percentile | RSI (m/s) | Your result |
|---|---|---|
| P10 | 1.12 | At or above |
| P25 | 1.67 | Below |
| P50 | 2.42 | Below |
| P75 | 3.32 | Below |
| P90 | 3.93 | Below |
| P95 | 4.35 | Below |
General drop-jump reference bands (protocol-specific)
| RSI (m/s) | Typical population |
|---|---|
| < 1.0 | Below typical general-population range |
| 1.0 - 1.5 | Adequate for general population |
| 1.5 - 2.5 | Trained athletes |
| > 2.5 | Highly trained / elite (varies by test) |
How it works & limitations
RSI vs RSI-modified
RSI = jump height (m) ÷ ground contact time (s), measured during a drop jump. It captures how quickly an athlete converts eccentric loading into concentric output - the quality at the heart of the fast stretch-shortening cycle. RSI-modified = jump height (m) ÷ time to takeoff (s), where time to takeoff runs from the start of the countermovement to toe-off, so it includes the slower pre-stretch phase. The two numbers are not interchangeable and have different typical ranges.
Why percentiles and ranges are protocol-specific
RSI changes with drop height, jump instruction and measurement device, so published values vary across tests and populations. The Plyomat percentiles come from device-measured per-athlete bests and are athlete references, not diagnostic thresholds. Use a fixed protocol - the same box height (commonly 20-45 cm), the same instruction and the same device - and compare an athlete against their own trend.
Dynamic Rebound Index (research stage)
DRI = (drop height + jump height in metres) ÷ (g x contact time2). It normalises rebound performance for the drop height used, which makes results from different box heights more comparable. It is an emerging research metric rather than an established normed test, so use it for within-athlete tracking and interpret it cautiously.
Sources
Last updated 2026-08-13
- Flanagan, E. P., & Comyns, T. M. (2008). The use of contact time and the reactive strength index to optimize fast stretch-shortening cycle training. Strength and Conditioning Journal, 30(5), 32-38.
- Ebben, W. P., & Petushek, E. J. (2010). Using the reactive strength index modified to evaluate plyometric performance. Journal of Strength and Conditioning Research, 24(8), 1983-1987.
- Plyomat. Vertical Jump Norms — RSI (per-athlete bests, 2026).
- Strength by Numbers. What is the Reactive Strength Index (RSI)?
Interpretation ranges are general references, not diagnostic thresholds. RSI alone should not be used to clear an athlete for training or return to sport.
Frequently asked questions
What is a good reactive strength index?
RSI is test- and drop-height-specific. For a drop jump, roughly 1.0-1.5 m/s is commonly considered an adequate score for the general population, trained athletes often reach 1.5-2.5 m/s and highly trained athletes can exceed 2.5 m/s. Track your own trend with a fixed protocol instead of comparing absolute numbers across tests.
Which drop height should I use?
A commonly used starting height is 30-45 cm. The key is consistency: the same drop height, same jump instruction and same measurement method every time, because RSI changes with drop height.