Reactive Strength Index Calculator

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.