Heart Rate Zone Calculator

Pure percentage multiplies your max heart rate by each zone's percentage, starting the scale from zero. Karvonen uses heart rate reserve (max HR minus resting HR), applies the zone percentage to that reserve, then adds resting HR back. Because Karvonen anchors every zone at your resting pulse, its targets land higher than the pure-percentage version. This calculator switches to Karvonen automatically once you enter a resting heart rate.

The 220 - age formula was never derived from a controlled study and can miss the mark by 10-20 bpm for any given person. That is why this calculator builds your zones from the Tanaka estimate (208 - 0.7 x age), which came from a meta-analysis of more than 18,000 subjects and tends to be more accurate, especially for adults over 40. Both numbers are population averages, so a lab or field max-effort test gives you your true value.

A common endurance prescription is roughly 80% of weekly volume in Zone 2 (aerobic base) and 20% in Zone 4-5 (threshold and VO2max intervals). Zone 1 fits active recovery and warm-ups. Zone 3 produces moderate fatigue without the highest training stimulus, so most coaches use it sparingly to avoid piling on unnecessary stress.

Not necessarily. Modern optical wrist sensors are accurate enough for steady efforts in Zones 1-3. For Zone 4-5 interval work, where heart rate spikes and drops quickly, a chest strap responds faster and gives more reliable readings to help you stay on target.

This calculator builds zones from the Tanaka estimate, so it has no field for a measured max HR. Individual max HR can vary by 10-20 bpm from any formula even among people of the same age, so if a lab test or true max-effort field test gave you a different number, treat the zones here as a starting estimate. To match your tested value exactly, apply the same zone percentages to your own max HR by hand.