Heart Rate Training Zones Calculator
Finds your target heart rate for each training zone using either the simple percentage-of-max method or the more precise Karvonen formula. Use it to structure cardio workouts for fat burning, aerobic base, or peak performance.
About this calculator
Your maximum heart rate (HRmax) is estimated as 220 − age. The simple method sets a zone boundary by multiplying HRmax by a target percentage: Zone HR = (220 − age) × zoneTarget. The Karvonen (heart rate reserve) method is more accurate because it factors in your resting heart rate (RHR), reflecting true cardiovascular fitness. The formula is: Zone HR = RHR + (zoneTarget × ((220 − age) − RHR)). The difference between HRmax and RHR is called the heart rate reserve (HRR). Karvonen targets are always higher than simple-percentage targets at the same intensity level, which is why trained athletes with low resting heart rates benefit most from using it. Common zones range from Zone 1 (~50–60% HRR) for recovery up to Zone 5 (~90–100% HRR) for maximum effort.
How to use
Assume age = 30, resting HR = 60 bpm, Karvonen method, Zone 3 target = 0.70 (70% HRR). Step 1 — estimate HRmax: 220 − 30 = 190 bpm. Step 2 — calculate HRR: 190 − 60 = 130 bpm. Step 3 — apply Karvonen: 60 + (0.70 × 130) = 60 + 91 = 151 bpm. Your Zone 3 lower boundary is 151 bpm. For comparison, the simple method gives 190 × 0.70 = 133 bpm — a meaningful 18 bpm difference that would lead to under-training if used for a fit individual.
Frequently asked questions
What is the difference between the Karvonen method and the simple percentage method for heart rate zones?
The simple method calculates a zone boundary as a fixed percentage of estimated maximum heart rate (220 − age). The Karvonen method instead uses heart rate reserve — the gap between your resting and maximum heart rate — giving a personalised result. Because a fit person has a lower resting heart rate, their heart rate reserve is larger, and Karvonen pushes zone boundaries higher to reflect genuine effort levels. Research consistently shows the Karvonen method correlates more closely with measured oxygen consumption (VO₂) at each intensity.
How accurate is the 220 minus age formula for estimating maximum heart rate?
The 220 − age formula is a population average with a standard deviation of about ±10–12 bpm, meaning your true HRmax could reasonably be 10 beats higher or lower. Factors like genetics, fitness level, and medication (e.g. beta-blockers) all influence actual HRmax. For greatest accuracy, perform a supervised maximal effort test on a treadmill or bike. However, for most recreational exercisers, 220 − age provides a safe and practical starting point.
Which heart rate zone is best for burning fat during cardio exercise?
Fat oxidation peaks in Zone 2, roughly 60–70% of heart rate reserve, where the body relies predominantly on aerobic metabolism fuelled by fat stores. Higher zones burn more total calories per minute but shift the fuel mix toward carbohydrates. For weight management, consistent Zone 2 training builds the aerobic base that improves fat-burning efficiency even at rest. Longer, lower-intensity sessions (45–90 minutes) in this zone are the cornerstone of many endurance and body-composition programmes.