Heart Rate Zone Calculator
Training in the right heart rate zone is one of the most effective ways to reach specific fitness goals. This calculator uses the Karvonen formula, which factors in your resting heart rate for more personalized and accurate zones than simple percentage-of-max methods.
The Karvonen formula calculates target heart rate as: THR = ((HRmax - HRrest) x %intensity) + HRrest. By using heart rate reserve (the difference between max and resting HR), the formula accounts for your individual fitness level.
The five standard training zones and their purposes:
Zone 1 (50-60% HRR) -- Recovery and warm-up. Very easy effort where you can hold a full conversation. Use this for warm-ups, cooldowns, and active recovery days.
Zone 2 (60-70% HRR) -- Aerobic endurance. Comfortable effort where you can talk in full sentences. This is where you build your aerobic base and burn the highest percentage of calories from fat. Most of your training should happen here.
Zone 3 (70-80% HRR) -- Tempo. Moderately hard effort where conversation becomes choppy. Improves aerobic capacity and running economy. Tempo runs and steady-state cardio live in this zone.
Zone 4 (80-90% HRR) -- Threshold. Hard effort where you can only say a few words at a time. This trains your lactate threshold, the intensity above which fatigue accumulates rapidly. Intervals and race-pace work happen here.
Zone 5 (90-100% HRR) -- VO2max. Maximum effort sustainable for only 1-5 minutes. Used for short, intense intervals to develop peak aerobic power. Only a small percentage of your training should be in this zone.
A well-structured training plan follows the 80/20 rule: about 80% of your training time in zones 1-2 (easy) and 20% in zones 3-5 (moderate to hard).