Heart Rate Zone Calculator
Calculates your target heart rate for a given exercise intensity using your age-predicted maximum heart rate. Use it to stay in the right training zone for fat burning, cardio fitness, or peak performance.
About this calculator
Your maximum heart rate (MHR) is the highest number of beats per minute your heart can achieve during all-out effort. The most widely used estimate is the age-based formula: MHR = 220 − age. Target heart rate for a specific exercise intensity is then calculated as: Target HR = (220 − age) × (intensity / 100). For example, training at 70% intensity means your heart should beat at 70% of MHR. Common training zones include 50–60% (light/recovery), 60–70% (fat-burning), 70–80% (aerobic/cardio), 80–90% (anaerobic threshold), and 90–100% (maximum effort). Staying within these zones helps athletes and fitness enthusiasts optimise workouts, avoid overtraining, and achieve specific physiological adaptations.
How to use
Suppose a 35-year-old wants to train at 75% intensity (aerobic zone). First, calculate MHR: 220 − 35 = 185 bpm. Then apply the intensity: Target HR = 185 × (75 / 100) = 185 × 0.75 = 138.75 bpm, rounded to approximately 139 bpm. During their workout — whether running, cycling, or rowing — they should aim to keep their heart rate around 139 bpm using a chest strap or wrist-based heart rate monitor. This aerobic zone promotes cardiovascular endurance and efficient calorie burning.
Frequently asked questions
How do I find my target heart rate zone for fat burning?
The fat-burning zone is generally considered to be 60–70% of your maximum heart rate. At this moderate intensity, the body relies more heavily on fat as a fuel source relative to carbohydrates, though total calorie burn is lower than at higher intensities. To find your fat-burning range, calculate MHR = 220 − age, then multiply by 0.60 and 0.70 to get the lower and upper bounds. For a 40-year-old, that would be 180 × 0.60 = 108 bpm to 180 × 0.70 = 126 bpm. Wearing a heart rate monitor during exercise is the easiest way to stay in this range.
Why is the 220 minus age formula used to estimate maximum heart rate?
The 220 − age formula is a population-derived approximation first popularised in the 1970s based on data compiled by Haskell and Fox. It is convenient because it requires no equipment and gives a reasonable estimate for most healthy adults. However, the formula has a standard deviation of roughly ±10–12 bpm, meaning individual MHR can differ significantly from the predicted value. More accurate estimates can be obtained from graded exercise tests (e.g., a treadmill stress test) conducted under medical supervision. Athletes and older adults in particular may find the formula less reliable.
What happens if you consistently exercise above your target heart rate zone?
Training chronically above your target zone — particularly in the 90–100% range — without adequate recovery increases the risk of overtraining syndrome, characterised by fatigue, decreased performance, elevated resting heart rate, and increased injury susceptibility. Short high-intensity bursts (HIIT) above 85% MHR are beneficial when programmed correctly, but prolonged sessions in this range place excessive stress on the cardiovascular and musculoskeletal systems. For most recreational exercisers, spending the majority of training time (roughly 80%) at moderate intensities (65–75% MHR) and only 20% at high intensities produces the best long-term fitness gains — a principle known as polarised training.