Reactive Strength Index Calculator
Your RSI from jump height and contact time
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milliseconds on the ground, e.g. 200
Reactive Strength Index Calculator
The Reactive Strength Index is the go-to field test of explosive, reactive power for jumpers and sprinters. Enter your drop-jump height and your ground contact time, and this calculator returns your RSI — jump height divided by contact time — plus a rating band. Use it to monitor plyometric training, manage neuromuscular fatigue, and compare reactive ability between athletes.
The Reactive Strength Index (RSI) measures how well you tolerate and reuse impact: jump height divided by ground contact time, from a drop jump. Higher RSI means a more explosive, springier stretch-shortening cycle. Typical guide values: under 0.5 low, around 1.0 average, 1.5–2.5 good, above 2.5 elite. Measure contact time with a jump mat or force plate and keep the drop height the same to track change.
Frequently Asked Questions
- What is the Reactive Strength Index (RSI)?
- RSI measures explosive, reactive power, how well you absorb and rebound from landing. It is calculated from a drop jump and reflects your ability to produce force quickly, a key quality for sprinting, jumping, and other fast stretch-shortening movements.
- How is RSI calculated?
- RSI = jump height / ground contact time, both during a drop jump. Enter your jump height and the time your feet spend on the ground between landing and take-off, and the calculator returns your RSI along with a rating.
- What is a good RSI value?
- RSI is typically expressed in metres per second; values around 1.5-2.0 are good and above roughly 2.5-3.0 indicate excellent reactive strength, while below 1.5 suggests room to improve. The aim is high jump height with minimal ground contact time.