What is Heart Rate Reserve (HRR)?

HRR is the difference between your maximum heart rate and your resting heart rate (HRR = MaxHR − RestHR). It represents the range your heart can work through during exercise. A larger HRR generally indicates better cardiovascular fitness.

How is the Karvonen formula different from percentage of max HR?

The Karvonen method anchors zones to your HRR rather than zero, so resting HR is factored in. Two people with the same max HR but different resting HRs (one sedentary, one trained) will get different targets. This makes zones more accurate for individuals at varying fitness levels.

Which max HR formula should I use?

Fox (220 − age) is the most common and works for general populations. Tanaka (208 − 0.7 × age) is considered more accurate for adults over 40 based on a large meta-analysis. Gulati (206 − 0.88 × age) was derived from women and tends to give lower estimates for females. If you have a measured max HR from a true maximal effort, use that — it beats any formula.

How do I accurately measure resting heart rate?

Measure first thing in the morning before standing up. Lie still for a few minutes, then count heartbeats for 60 seconds (or 30 seconds × 2). Average three consecutive morning readings for best accuracy. Typical resting HR is 60–80 BPM; trained endurance athletes often fall below 50 BPM.

What do the five training zones mean?

Zone 1 (50–60% HRR): light recovery and warm-up. Zone 2 (60–70% HRR): aerobic base, fat oxidation, long steady-state work. Zone 3 (70–80% HRR): tempo, moderate aerobic development. Zone 4 (80–90% HRR): lactate threshold, race-pace efforts. Zone 5 (90–100% HRR): VO2max intervals and maximal sprints.

Can I use this calculator if I do not know my exact max HR?

Yes. Use the age-based estimator to get an approximate max HR with one of three formulas. The estimate has ±10–15 BPM individual variation, so treat the resulting zones as starting points and adjust based on perceived effort over a few weeks of training.

Heart Rate Reserve Calculator

Enter resting and max heart rate to get your Heart Rate Reserve and five Karvonen target training zones.

Heart Rate Inputs

Resting Heart Rate (BPM)

Measured lying still, before getting up in the morning.

Maximum Heart Rate (BPM)

From a lab test or a maximal field effort. Use the estimator below if unknown.

Estimate Max HR from Age

Results

Resting HR

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BPM

Max HR

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BPM

HRR

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BPM

Enter values above and click Calculate.

Summary

Heart Rate Reserve (HRR) is the gap between your maximum and resting heart rate — and it is the foundation of the Karvonen method for setting personalized training zones. This calculator computes your HRR and five Karvonen intensity zones, and lets you estimate max HR from age using the Fox, Tanaka, or Gulati formulas when a measured value is not available. The result is a set of BPM targets you can program directly into a heart rate monitor or use to guide effort during any aerobic workout.

How it works

Enter your resting heart rate (measured lying still, ideally before getting out of bed).
Enter your maximum heart rate from a lab test or a hard field effort.
Optionally estimate max HR from age using Fox (220 − age), Tanaka (208 − 0.7 × age), or Gulati (206 − 0.88 × age for women) formulas.
The calculator subtracts resting HR from max HR to get your Heart Rate Reserve (HRR).
Karvonen target zones are calculated as: RestingHR + (Intensity% × HRR) for five intensity bands.
Review the BPM range for each zone and use them to guide your workout intensity.

Use cases

Program Garmin, Polar, or Apple Watch heart rate zones from personalized HRR data.
Design aerobic base-building sessions in Zone 2 without drifting into Zone 3.
Find your lactate-threshold zone (Zone 4) for tempo runs and cycling time trials.
Compare max-HR-percentage zones versus Karvonen HRR zones side by side.
Re-calibrate zones after fitness improves and resting HR decreases.
Choose the right max-HR formula for age, sex, or sport.
Coach athletes by providing exact BPM targets for each workout type.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu