What are the 5 heart rate training zones?

Zone 1 (50–60% MHR): Recovery and warm-up. Zone 2 (60–70%): Fat burning and base endurance. Zone 3 (70–80%): Aerobic and tempo. Zone 4 (80–90%): Anaerobic threshold and lactate training. Zone 5 (90–100%): Maximum effort and sprints.

Which zone burns the most fat?

Zone 2 (60–70% MHR) burns the highest proportion of calories from fat, but Zone 3–4 burns more total calories per minute. For weight loss, total calorie expenditure matters more than fat-burn percentage.

How much time should I spend in each zone?

Most endurance coaches recommend the 80/20 rule: 80% of training in Zone 1–2 (low intensity) and 20% in Zone 3–5 (higher intensity). This approach builds aerobic base while avoiding overtraining.

Is my data sent to a server?

All calculations are pure JavaScript running in your browser. Our servers are not involved at any point.

Heart rate zone calculator

Enter your age to calculate your 5 heart rate training zones, from recovery to maximum effort. Add your resting heart rate to use the Karvonen method for more personalised zones. Each zone corresponds to a specific intensity and training benefit.

Age (years)

Resting heart rate (bpm) optional

How it works

Maximum heart rate is estimated using the Tanaka formula: Max HR = 208 − (0.7 × age). Each training zone is a percentage range of max HR. When a resting heart rate is provided, the Karvonen method is used instead: Target HR = ((Max HR − Resting HR) × intensity%) + Resting HR. This accounts for heart rate reserve and produces personalised zones. All arithmetic runs locally in your browser using pure JavaScript.

Processing runs in your browser

All calculations happen locally using pure JavaScript. Our servers are not involved at any point.

Technical specification

The Tanaka formula (208 − 0.7 × age) was derived from a meta-analysis of 351 studies involving 18,712 subjects by Tanaka et al. and published in the Journal of the American College of Cardiology 37:1 (2001). It is more accurate than the classic 220 − age formula across all age groups, particularly for adults over 40. Both formulas have a standard deviation of ±10–12 bpm. The Karvonen method uses heart rate reserve (HRR = Max HR − Resting HR) to scale zones relative to individual fitness.

Max HR formula: Tanaka: 208 − 0.7 × age (JACC 37:1, 2001)
Personalised zones: Karvonen method using heart rate reserve
Accuracy: ±10–12 bpm (population average)
Browser API: Pure JavaScript arithmetic. No library

Related operations

For estimating daily energy expenditure for training, try the calorie calculator. To capture a baseline weight category, use the BMI calculator. For tracking strength gains alongside cardio zones, see the one-rep max calculator.

Frequently asked questions

What are the 5 heart rate training zones?: Zone 1 (50–60% MHR): Recovery and warm-up. Zone 2 (60–70%): Fat burning and base endurance. Zone 3 (70–80%): Aerobic and tempo. Zone 4 (80–90%): Anaerobic threshold and lactate training. Zone 5 (90–100%): Maximum effort and sprints.
Which zone burns the most fat?: Zone 2 (60–70% MHR) burns the highest proportion of calories from fat, but Zone 3–4 burns more total calories per minute. For weight loss, total calorie expenditure matters more than fat-burn percentage.
How much time should I spend in each zone?: Most endurance coaches recommend the 80/20 rule: 80% of training in Zone 1–2 (low intensity) and 20% in Zone 3–5 (higher intensity). This approach builds aerobic base while avoiding overtraining.
Is my data sent to a server?: All calculations are pure JavaScript running in your browser. Our servers are not involved at any point.

Last reviewed May 26, 2026