Heart Rate Zone Calculator

Heart rate training zones are worked out as percentages of your maximum heart rate, and the simplest estimate of that maximum is 220 minus your age. The calculator then divides the range between your resting heart rate and your maximum into five bands. Zone 1 sits at 50 to 60% and covers warm-up, Zone 2 at 60 to 70% is the fat-burning band, Zone 3 at 70 to 80% is aerobic work, Zone 4 at 80 to 90% is threshold effort, and Zone 5 from 90 to 100% is where VO2 max training happens.

For greater accuracy, the Karvonen method uses your resting heart rate to calculate a heart rate reserve, meaning your maximum minus your resting rate, then applies the zone percentages to that reserve and adds the resting rate back on. This produces personalised zones that reflect your fitness rather than your age alone. The 220 minus age shortcut is a population average and misses for plenty of people: very fit individuals often sit 5 to 10 bpm above it, and some genetic variants land 10 to 20 bpm either side. Tanaka's version, 208 minus 0.7 times your age, is generally closer, giving 187 bpm at age 30 where the older formula gives 190.

Effort is often easier to judge by how you talk than by the numbers on a watch. Zone 1 is genuinely easy and fully conversational. Zone 2 can be held for hours while you speak in full sentences. Zone 3 reduces you to phrases of two or three words, Zone 4 to single words and about an hour at most, and Zone 5 is anaerobic and measured in minutes. Runners can map it to race pace: marathon pace sits at the top of Zone 2 or the bottom of Zone 3, 10K pace lands in the middle of Zone 4, and 5K pace at the top of Zone 4 or the bottom of Zone 5.

Zone 2 training is recommended for building an aerobic base and efficient fat oxidation, since long easy work develops mitochondria, capillaries and fat-burning capacity. The NHS recommends at least 150 minutes of moderate-intensity activity per week, roughly Zone 2 to 3, or 75 minutes of vigorous activity in Zone 4 to 5. Elite athletes follow an 80/20 split, keeping 80% of training easy in Zones 1 and 2 and 20% hard in Zones 4 and 5, where sprint intervals build VO2 max and lactate threshold. Most amateurs do the reverse and accumulate medium-effort Zone 3 work that neither builds the base nor raises the ceiling.

Enter your age and resting heart rate to see your personalised zones. That resting figure is worth watching in its own right. Adults average 60 to 100 bpm, trained athletes sit at 40 to 60, and elite endurance athletes reach 30 to 40. Measure it first thing in the morning before you stand up, or let a watch record it automatically, and expect it to drift down over months of training. A sudden rise of 5 bpm or more at rest usually points to overtraining, illness, dehydration or stress. NHS guidance is to see a GP if your resting rate stays above 100 bpm, or if it is under 60 alongside dizziness or fatigue, which can indicate bradycardia.

Chest straps such as the Polar H10 or Garmin HRM-Pro cost £40 to £100 and give the most reliable readings, typically within 1 to 2 bpm of a medical-grade ECG. Optical wrist sensors on an Apple Watch, Garmin or Fitbit are more convenient but less accurate during intervals. Strava, Garmin Connect and Polar Flow all sync the data off the device. Heart rate variability, the gap between individual beats, is tracked by WHOOP and the Oura ring as a recovery marker. The NHS app gives a rough free check using a finger on the phone camera, and a graded treadmill test with breath gas analysis costs £100 to £300 privately if you want a measured maximum.