Calculate your 5 heart rate training zones using the Karvonen formula — for optimal fat burning, aerobic fitness, lactate threshold and VO2 max training.
Enter your figures and click Calculate to see your results.
Enter your age and resting heart rate — the Karvonen formula uses both for more accurate personalised training zones.
Press the Calculate button. Results appear instantly using standard clinical and scientific formulas.
Results are displayed with all key values clearly labelled. Use the Copy button to grab your results or Download to save a text file. For health decisions, always consult a healthcare professional.
Heart rate zones divide cardio effort into five intensity bands. Zone 1 (50–60% MHR): easy recovery. Zone 2 (60–70%): fat burning, aerobic base building. Zone 3 (70–80%): aerobic fitness. Zone 4 (80–90%): lactate threshold, improving pace. Zone 5 (90–100%): VO2 max, sprinting. Different zones produce different fitness adaptations.
The standard formula is 220 − age. A more accurate estimate is 208 − (0.7 × age). For the most precise result, perform a field test: after a proper warm-up, run all-out for 60 seconds up a hill and record the peak heart rate reached. Max HR varies by ±10–20 bpm between individuals of the same age.
The Karvonen (Heart Rate Reserve) formula gives more personalised zones by accounting for your resting heart rate: Target HR = Resting HR + (percentage × Heart Rate Reserve), where HRR = Max HR − Resting HR. This produces different zones for fit vs unfit individuals of the same age, making it more individualised than simple MHR percentages.
Zone 2 (60–70% MHR) is called the "fat burning zone" because fat is the primary fuel. However, higher-intensity zones burn more total calories per minute. For fat loss, a combination works best: Zone 2 for aerobic base and recovery volume, with Zone 4–5 interval sessions for metabolic impact. Total calorie deficit matters more than which zone you train in.
Research on elite endurance athletes shows that about 80% of their training is done at low intensity (Zones 1–2) and only 20% at high intensity (Zones 4–5). This polarised approach avoids the "grey zone" of moderate intensity, which is too hard for full recovery but not hard enough to produce strong adaptations. It maximises both volume and quality.
