How It Works
The calculator uses the widely adopted formula for estimating maximum heart rate:
Max Heart Rate = 220 - Age
Once the MHR is known, five training zones are derived by applying percentage ranges to that maximum. Zone 1 covers 50-60% of MHR (recovery pace), Zone 2 is 60-70% (fat burn), Zone 3 is 70-80% (aerobic conditioning), Zone 4 is 80-90% (anaerobic threshold), and Zone 5 is 90-100% (peak effort). If a resting heart rate is provided, the calculator also computes Karvonen-adjusted zones using heart rate reserve (HRR = MHR - Resting HR) for more personalized ranges.
Variable Definitions
Age is your current age in whole years. This is the only required input. The 220-minus-age formula was derived from large population studies and provides an average estimate. Individual variation is significant — roughly plus or minus 10-12 bpm — so treat the output as a guideline. A common mistake is using your age at the start of the year rather than your current age, though the difference is negligible.
Resting Heart Rate is your pulse when completely at rest, measured in beats per minute. The ideal measurement is taken first thing in the morning before getting out of bed, averaged over three days. Normal resting rates for adults range from 60 to 100 bpm, while trained endurance athletes may have rates in the low 40s. Entering this value enables Karvonen-adjusted zones, which are more accurate for individuals whose resting rate deviates from the population average of about 72 bpm.
Fitness Level is a self-reported assessment of your current training status. This input adjusts the descriptive text alongside each zone — a beginner is advised to spend more time in Zones 1-2, while an advanced athlete will do structured work in Zones 3-4. The zone BPM ranges themselves do not change based on fitness level; only the recommendations do.
Edge Cases and Advanced Scenarios
How zones shift for trained athletes vs beginners: A trained athlete with a resting heart rate of 48 bpm and a beginner with a resting rate of 80 bpm will have the same MHR if they are the same age. But their Karvonen zones differ substantially. The athlete's Zone 2 spans a different absolute BPM range than the beginner's Zone 2. This means the athlete can sustain a higher absolute heart rate while staying in the same relative intensity zone. If standard zones feel too easy, switching to Karvonen zones provides a more meaningful training framework.
Medications that affect heart rate: Beta-blockers, calcium channel blockers, and some anti-anxiety medications suppress heart rate, making the 220-minus-age formula inaccurate. If you take heart rate-lowering medication, your actual MHR during exercise will be lower than the formula predicts. A supervised graded exercise test is the only reliable way to determine your zones in this case.
What to Do with Your Result
Set your watch zones. Most running watches and fitness trackers let you enter custom heart rate zones. Copy the BPM ranges from this calculator into your device settings so your real-time zone alerts match your physiology.
Structure your training week. A common endurance framework is 80/20: spend 80% of training time in Zones 1-2 and 20% in Zones 3-5. This polarized approach builds aerobic base while developing speed.
Track resting heart rate over time. As cardiovascular fitness improves, resting heart rate typically decreases. Measuring it weekly gives you an objective fitness trend. A sudden spike can signal overtraining, illness, or poor recovery.
Validate with a real test. If you train seriously, consider a lab-based VO2max or graded exercise test to find your true MHR. The 220-minus-age estimate is a starting point — knowing your real maximum lets you dial in zones with precision.