Heart Rate Zone Calculator

Heart rate training zones divide your exercise intensity into numbered bands based on percentages of your maximum heart rate (MHR). Most systems use 5 zones: Zone 1 (50-60% MHR) · very light, warm-up/recovery; Zone 2 (60-70%) · easy aerobic, fat burning, conversation possible; Zone 3 (70-80%) · aerobic, moderate effort; Zone 4 (80-90%) · threshold, hard effort, builds speed and lactate tolerance; Zone 5 (90-100%) · maximal, sprint efforts.

Zone 2 (approximately 60-70% of MHR) has the highest proportion of fat as fuel, which is why it is often called the 'fat-burning zone'. However, higher-intensity zones burn more total calories per unit of time, which generally leads to greater total fat loss over time. For long-term body composition goals, a combination of Zone 2 for aerobic base and Zone 4-5 intervals for calorie expenditure is most effective.

Most endurance coaches recommend a 'polarised' or '80/20' approach: roughly 80% of training time in easy, low-intensity zones (Zone 1-2) and about 20% in high-intensity zones (Zone 4-5), with relatively little time in the moderate 'grey zone' (Zone 3). This maximises aerobic development while managing fatigue and recovery. Zone training requires a heart rate monitor for real-time feedback; chest strap monitors are more accurate than wrist-based optical sensors.