Target Heart Rate Calculator

Target heart rate (THR) is the desired heart rate range during exercise to achieve a specific training goal. Different intensity zones produce different physiological adaptations: low zones (50–60% MHR) burn fat and aid recovery; moderate zones (60–80% MHR) build aerobic endurance; high zones (80–100% MHR) improve VO₂ max, speed, and anaerobic capacity.

The Karvonen formula (Heart Rate Reserve method) calculates target HR as: THR = ((MHR − RHR) × intensity%) + RHR. It accounts for resting heart rate (RHR), giving more personalised zones than simple % of MHR. Two people with the same MHR but different RHRs (60 vs 80 bpm) will have meaningfully different effective training zones using this method.

The fat-burning zone is typically 60–70% of MHR. At this intensity, a higher proportion of calories come from fat. However, higher-intensity exercise burns more total calories, which often leads to greater overall fat loss. The fat-burning zone is best for long steady-state sessions and for those new to exercise who need to build aerobic base before attempting higher-intensity work.

Measure your resting heart rate first thing in the morning before getting out of bed. Place two fingers on your wrist (radial artery) or neck (carotid artery) and count beats for 60 seconds. Take readings on 3 consecutive mornings and average them. Normal adult RHR is 60–100 bpm; well-trained athletes can have RHRs of 40–55 bpm. Fitness wearables can also track this automatically overnight.

Heart rate reserve (HRR) is the difference between your maximum heart rate and your resting heart rate: HRR = MHR − RHR. It represents your cardiovascular working capacity. The Karvonen formula uses HRR to anchor training zones to your actual working heart rate range. Higher HRR (low resting HR + age-appropriate max HR) is associated with better cardiovascular fitness.