HRV Calculator
RMSSD, SDNN and pNN50 from RR intervals.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use HRV Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Add RR intervals (in ms) — at least 2 needed.
- 2
Step 2. Remove any with the × button.
- 3
Step 3. Read RMSSD (with fitness rating), SDNN, pNN50 and average HR.
Why use this tool
Frequently asked questions
Everything you might want to know about hrv calculator.
Resting Heart Rate Checker
RHR fitness rating with reference ranges by age.
Heart Rate Zones
Five training zones via Karvonen or % of max HR.
Blood Pressure Checker
Classify your BP reading using American Heart Association categories.
VO₂max Calculator
Aerobic capacity from Cooper 12-min run or resting HR.