Heart Rate Zone Calculator

Heart Rate Zone Calculator — Find Your Training Zones Using the Karvonen Formula

Training without knowing your heart rate zones is like driving without a speedometer — you might be going fast enough, or you might be spinning your wheels at the wrong intensity for your fitness goal. Heart rate zones give you objective targets for each workout: Zone 2 for aerobic base building and fat metabolism, Zone 4 for lactate threshold training that improves race pace, Zone 5 for high-intensity intervals that build peak power. This calculator gives you personalised BPM targets for all five zones using either the Karvonen formula or simple percentage of max HR, both referenced in exercise-intensity guidance from the American College of Sports Medicine (ACSM).

How to calculate your heart rate zones

Enter your age — the calculator uses the standard Max HR = 220 − age formula as a starting point. If you know your actual maximum heart rate from a fitness test or wearable device, enter it directly for more accurate results. Enter your resting heart rate (measure it first thing in the morning before getting out of bed, across three days and average the readings — a typical resting HR is 60–80 BPM for sedentary adults and 40–60 BPM for trained athletes). Select your calculation method: Karvonen (accounts for resting heart rate, which many people find more individual) or Percentage of Max HR (simpler, used by many training apps). Your five training zones appear immediately with BPM ranges and descriptions of what physiological adaptations each zone targets.

What each heart rate training zone does

Zone 1 (50–60% of max HR, or of heart rate reserve in Karvonen mode) is very light activity — warm-up, cool-down, and active recovery between hard sessions. Zone 2 (60–70%) is the aerobic base zone, sometimes called the "fat burning zone" because a higher proportion of fuel comes from fat oxidation at this intensity, although total energy balance matters more for weight loss. This is where much endurance training volume is often accumulated. The same percentages apply to heart rate reserve in Karvonen mode and to max HR in the simple mode. Zone 3 (70–80%) is moderate aerobic work — sustainable for 30–60 minutes, builds cardiovascular efficiency. Zone 4 (80–90%) is the lactate threshold zone — training here improves your ability to sustain faster paces. Zone 5 (90–100%) is maximum effort — used in HIIT intervals, sprint training, and race efforts of under 8 minutes.

Who uses this tool

Runners training for 5K to marathon distances use it to set precise targets for easy long runs (Zone 2), tempo workouts (Zone 4), and VO2max intervals (Zone 5). Cyclists use it to set training zones that match their training plan's prescribed intensities. Gym members doing group fitness classes use it to understand whether the class they are attending is aerobic conditioning or high-intensity work. Coaches use it to set individualised targets for athletes rather than using the same generic percentage for everyone.

Privacy and data handling

All heart rate calculations run in your browser — your age, resting heart rate, and max HR data are never sent to any server.