Heart Rate Variability Calculator

Work out heart rate variability instantly with clear inputs, formula shown and shareable results.

About Heart Rate Variability Calculator

RMSSD is the root mean square of successive differences between heartbeats and is the standard short-recording measure of parasympathetic activity. Because it is log-normally distributed, apps report the natural log scaled to a 0-100 score - 20 x ln(RMSSD) here. RMSSD declines roughly 0.5 ms per year after age 20, so comparisons must be age-adjusted.

Formulas

HRV score

score = 20 x ln(RMSSD)

Age expectation

typical RMSSD is about 60 - 0.5 x (age - 20) ms

Worked example

With the default values below, Heart Rate Variability Calculator returns HRV Score of 74.8. Change any input above and every figure here is recalculated in your browser.

Inputs used

Measured RMSSDminimum 1 ms: 42 ms
Ageaccepts 10–100 years: 35 years

Results

HRV Score: 74.8 /100
Natural Log Of RMSSD: 3.738
Typical RMSSD For Your Age: 52.5 ms
Interpretation: Within the typical range for your age

Step by step

1Values used
2HRV score
3Age expectation
4HRV Score= 74.8 /100
5Natural Log Of RMSSD= 3.738
6Typical RMSSD For Your Age= 52.5 ms
7Interpretation= Within the typical range for your age

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.
This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.

Frequently Asked Questions

Why is HRV reported on a log scale?

Because raw RMSSD is heavily skewed, so a 10 ms change means something very different at 20 ms than at 80 ms. Logging makes changes comparable.

What matters more, absolute value or trend?

The trend against your own baseline. Absolute HRV varies enormously between individuals and is nearly useless for comparison.