Maximum Heart Rate Calculator — HRmax and Karvonen zones

Maximum heart rate (HRmax) is the highest number of heartbeats per minute the body can achieve during maximum physical exertion. The most common formula is Fox: HRmax = 220 - age. For a 35-year-old, HRmax = 185 bpm. The formula is a statistical approximation — actual HRmax can be measured more accurately with a supervised exercise stress test.

Fox (220 - age) is the simplest and most widely used but may underestimate HRmax in older adults. Tanaka (208 - 0.7 x age) is more precise for people over 40 and is derived from a large meta-analysis. Gulati (206 - 0.88 x age) was developed specifically for women and accounts for sex-based differences in exercise physiology.

The Karvonen method incorporates resting heart rate (HRrest) and bases zones on heart rate reserve (HRR = HRmax - HRrest): HR_zone = HRR x intensity% + HRrest. This makes zones more personalised than simply multiplying HRmax by a percentage. For example, HRmax = 190, HRrest = 60, HRR = 130; Zone 1 (50-60%): 125-138 bpm.

Heart rate reserve (HRR) is the difference between maximum and resting heart rate: HRR = HRmax - HRrest. A larger reserve indicates a better-conditioned cardiovascular system. Well-trained athletes often have low HRrest (40-50 bpm), which increases HRR and allows more precise Karvonen zones.

Zone 1 (50-60% HRR): recovery, light walking, very low intensity. Zone 2 (60-70%): fat burning, comfortable pace, can hold a conversation. Zone 3 (70-80%): aerobic, improves endurance, breathing faster but steady. Zone 4 (80-90%): lactate threshold, hard effort, difficult to talk. Zone 5 (90-100%): maximum intensity, short sprints and intervals.

The most accurate resting heart rate measurement is taken in the morning immediately after waking, before getting out of bed. Count beats for 60 seconds or 30 seconds and multiply by 2. Normal adult resting HR is 60-100 bpm. Athletes often have HRrest below 60 bpm, and highly trained runners even 40-50 bpm.

The Gulati formula (HRmax = 206 - 0.88 x age) was derived from studies conducted on women and accounts for physiological sex differences. Women tend to have slightly higher HRmax than predicted by Fox for the same age. Physically active women should consider using Gulati for more accurate training zones.

Yes — HRmax naturally decreases with age by approximately 1 bpm per year. This is due to cardiovascular changes and is independent of fitness level. All formulas include age as the primary parameter. Regular training does not stop HRmax decline, but it keeps a high heart rate reserve by lowering resting HR.

Zone 2 (60-70% HRR) is often called the "fat burning zone" because the body derives the highest percentage of energy from fat. However, Zones 3 and 4 produce a higher total calorie expenditure. For weight loss, an optimal combination is longer sessions in Zone 2 combined with short intense sessions in Zones 3-4.

No — the calculator provides indicative values based on statistical formulas and is not medical advice. Before intensive training, especially after age 35 or with heart disease, hypertension, diabetes or other conditions, consult a physician and undergo an ECG exercise stress test. The stress test will give precise, personalised heart rate zones and assess training safety.