Heart Rate Zone Calculator
Calculate your personalised heart rate training zones using both percentage of max HR and the Karvonen (heart rate reserve) method. Free, instant, accurate.
All calculations run instantly in your browser. No data is sent to any server.
Disclaimer: Results are for informational purposes only and do not constitute medical advice, diagnosis, or treatment. Consult a qualified healthcare professional for personal guidance.
Zone 2 and Aerobic Base Training
Zone 2 (60–70% MHR) has attracted significant research attention because it develops mitochondrial density and aerobic capacity without the accumulated fatigue that higher-intensity work generates. Elite endurance athletes spend 70–80% of their total training volume in Zone 2. For health benefits, 150 minutes of Zone 2 activity per week meets WHO guidelines for moderate-intensity aerobic exercise.
Karvonen vs. Flat Percentage
The flat percentage method (e.g., Zone 2 = 60–70% of MHR) is simple but does not account for fitness level. The Karvonen formula uses Heart Rate Reserve (HRR = MHR − resting HR), which means a fitter person with a lower resting HR (e.g., 45 bpm) gets higher absolute zone targets than a deconditioned person of the same age and MHR. For trained individuals, Karvonen zones are generally more accurate.
FAQs
What are heart rate zones?
Intensity bands based on % of MHR. 5-zone model: 50–60% (recovery), 60–70% (aerobic base), 70–80% (aerobic), 80–90% (threshold), 90–100% (max).
What is Karvonen formula?
Target HR = resting HR + (% × (MHR − resting HR)). Accounts for individual fitness via heart rate reserve. More accurate for trained individuals.