Target Heart Rate Zone Calculator

The Formula

Heart rate training zones use either a simple percentage of max HR or the Karvonen Heart Rate Reserve method, which factors in resting HR for significantly more personalized zones.

Variable Definitions

How to Use This Calculator

1. 1

   Enter your age to get your estimated max heart rate.

2. 2

   Enter your resting heart rate for the more accurate Karvonen formula (measure it first thing in the morning).

3. 3

   Select your calculation method — Karvonen is recommended when resting HR is available.

4. 4

   Review all five training zones with their BPM ranges and training purposes.

5. 5

   Use the 80/20 rule to structure your weekly training volume across zones.

Common Applications

• Endurance training optimization — use Zone 2 (fat burn / aerobic base) to build aerobic capacity with minimal recovery cost, following the 80/20 polarized training approach
• Race pace strategy — determine the heart rate range for your goal race pace (e.g., marathon at Zone 2-3 boundary) to avoid starting too fast and fading late
• Fitness level assessment — track how your Karvonen heart rate reserve changes over time as your resting heart rate drops with improved cardiovascular fitness
• Interval training prescription — set target heart rates for Zone 4-5 high-intensity intervals and Zone 1 active recovery periods for structured speed work sessions

Heart rate zones range from recovery (50-60%) to max effort (90-100%); 80% of training in Zones 1-2

Understanding the Concept

Training in specific heart rate zones triggers different physiological adaptations. Zone 2 (fat burn / aerobic base) is the most underrated — training here builds aerobic capacity and fat-burning efficiency with minimal recovery cost. Zone 4–5 drives speed and VO2 Max improvements but requires more recovery time. Most recreational athletes spend too much time in Zone 3 — the "grey zone" — which is neither easy enough for optimal aerobic adaptation nor hard enough for performance gains. Elite endurance athletes follow the 80/20 rule: 80% of training in Zones 1–2 and only 20% in high-intensity Zones 4–5. This polarised training approach has been validated in studies of Olympic-level rowers, cyclists, and runners. A common practical application: for a runner doing 5 hours of weekly training, 4 hours should be easy (Zone 1–2, conversational pace) and 1 hour should be hard intervals (Zone 4–5). The 220 minus age formula for max heart rate has a standard deviation of ±10–12 bpm, meaning half the population's true max HR differs by more than 10 beats. The Karvonen method reduces this error by incorporating your resting heart rate, which adjusts for individual fitness level — a well-trained athlete might have a resting HR of 40 bpm while a sedentary person might have 75 bpm, leading to very different Heart Rate Reserve values and thus different training zones even at the same age.

Frequently Asked Questions

Sources & References