About Heart Rate Calculator

Calculate target heart rate zones for different exercise intensities. Part of the DevTools Surf developer suite. Browse more tools in the Calculators collection.

Use Cases

• Calculate personalized heart rate zones for a running or cycling training program.
• Determine fat-burning zone boundaries before a steady-state cardio session.
• Establish VO2 max zone boundaries for high-intensity interval training (HIIT) planning.
• Compare different max HR estimation formulas to understand the range of uncertainty.

Tips

• Use the Karvonen formula for more accurate training zones — it incorporates resting heart rate alongside max heart rate, unlike the simple percentage method.
• Measure your resting heart rate first thing in the morning before getting out of bed for the most accurate baseline.
• Zone 2 (60-70% of max) is the aerobic base zone — the most evidence-backed zone for cardiovascular adaptation with low injury risk.

Fun Facts

• The commonly cited maximum heart rate formula '220 minus age' was derived from an informal observation by Fox et al. in 1971 — it was never validated in a proper clinical study and has a standard deviation of ~12 bpm.
• A trained endurance athlete's resting heart rate can be as low as 28-40 bpm. Tour de France cyclists have recorded resting heart rates of 28 bpm (Miguel Indurain reportedly hit 28).
• Heart rate variability (HRV) — the millisecond variation between heartbeats — is a better fitness indicator than resting heart rate alone; higher HRV correlates with better cardiovascular fitness and recovery.

FAQ

Which formula does it use for max heart rate?

The default is 220 - age. You can switch to Tanaka (208 - 0.7 × age), which is better validated for adults over 40, or enter a measured max HR from a graded exercise test.

What are the five heart rate zones?

Zone 1: <60% (recovery), Zone 2: 60-70% (aerobic base), Zone 3: 70-80% (aerobic threshold), Zone 4: 80-90% (lactate threshold), Zone 5: >90% (VO2 max / anaerobic).

Is the Karvonen formula better?

For personalized zones, yes. Karvonen: Target HR = ((Max HR - Resting HR) × intensity%) + Resting HR. It accounts for individual fitness level; the simple percentage method treats everyone the same.