Heart rate zones from your maximum heart rate (220 − age, Tanaka, Gulati for women, or measured) by the Karvonen or percent-of-max method, with a target heart rate.
With a maximum of 180 bpm, 70 % intensity by the Karvonen (heart-rate reserve) method is about 144 bpm. Easy endurance work (zone 2) runs from 132 to 144 bpm.
| Zone | Intensity | From (bpm) | To (bpm) | Typical use |
|---|---|---|---|---|
| 1 · Very light | 50–60 % | 120 | 132 | Warm-up and recovery |
| 2 · Light | 60–70 % | 132 | 144 | Easy endurance |
| 3 · Moderate | 70–80 % | 144 | 156 | Aerobic fitness |
| 4 · Hard | 80–90 % | 156 | 168 | Threshold work |
| 5 · Maximum | 90–100 % | 168 | 180 | Short intervals |
Each zone applies the same formula at 50, 60, 70, 80, 90 and 100 % intensity.
Heart rates are shown as whole beats per minute, rounded half-up.
Maximum heart rate is estimated from age with 220 − age, Tanaka's 208 − 0.7 × age or, for women, Gulati's 206 − 0.88 × age, or entered from a test. Five training zones are then set between 50 and 100 % intensity in 10-point steps, either as a percent of maximum or by the Karvonen method, which applies the percentage to the heart-rate reserve (maximum minus resting rate) and adds the resting rate back.
Runners, cyclists and people following a cardio plan use the zones to pace sessions. For a 40-year-old with a resting heart rate of 60 bpm, the maximum is 180 bpm, and 70 % intensity by Karvonen is 144 bpm, the top of zone 2.
Age formulas predict a population average, and individual maximums scatter around it; Tanaka's pooled data showed that 220 − age underestimates the maximum in older adults. Beta blockers and some other medicines lower heart rate, so age-based zones do not fit people taking them.
Every zone is a percentage of maximum heart rate, so the formula behind the maximum moves every number after it. Four age formulas are in common use:
| Age | 220 − age | Tanaka | Gulati (women) | Nes |
|---|---|---|---|---|
| 20 | 200 | 194 | 188 | 198 |
| 30 | 190 | 187 | 180 | 192 |
| 40 | 180 | 180 | 171 | 185 |
| 50 | 170 | 173 | 162 | 179 |
| 60 | 160 | 166 | 153 | 173 |
| 70 | 150 | 159 | 144 | 166 |
| 80 | 140 | 152 | 136 | 160 |
Values are in beats per minute, rounded half-up. 220 − age and Tanaka cross at 40 and separate by 0.3 bpm for each year either side, so at 80 Tanaka is 12 bpm higher. The calculator offers the first three. To use Nes, work out the maximum and enter it under "My measured maximum"; the field accepts decimals, such as 185.4 for Nes at age 40.
A 55-year-old woman with a resting heart rate of 62 bpm wants to train at 70 % intensity.
As a plain percentage of maximum, 70 % is 169.5 × 0.70 = 118.65, or 119 bpm, which is 18 bpm lower. The two methods agree only at 100 %. Karvonen's 60 % is 126.5 bpm, or 74.6 % of her maximum, so a zone labelled "60–70 %" sits higher under Karvonen than under percent of maximum. Check which method a watch or app uses before comparing its numbers with these.
With Gulati's formula her maximum is 206 − 0.88 × 55 = 157.6 bpm, and the 70 % Karvonen target falls to 128.92, displayed as 129 bpm: 8 bpm below the Tanaka result.
The calculator's five zones are 10-point bands from 50 to 100 % intensity. For the same woman (Tanaka maximum 169.5 bpm, resting rate 62 bpm):
| Zone | Intensity | Karvonen (bpm) | Percent of max (bpm) |
|---|---|---|---|
| 1 · Very light | 50–60 % | 116–127 | 85–102 |
| 2 · Light | 60–70 % | 127–137 | 102–119 |
| 3 · Moderate | 70–80 % | 137–148 | 119–136 |
| 4 · Hard | 80–90 % | 148–159 | 136–153 |
| 5 · Maximum | 90–100 % | 159–170 | 153–170 |
Each bound is rounded half-up, so 126.5 shows as 127, and neighbouring zones share their boundary beat. Under Karvonen each of her zones is 10.75 bpm wide (10 % of a 107.5 bpm reserve); by percent of maximum, 16.95 bpm. The bottom of Karvonen zone 1, 116 bpm, is already 68 % of her maximum.
Age predicts the average for a group well and the maximum for one person poorly. The HUNT study put the standard error of its formula at 10.8 bpm, and Robergs and Landwehr found errors of 7 to 11 bpm across two decades of prediction equations. At 70 % Karvonen intensity, a maximum that is 10.8 bpm too high raises the target by 0.7 × 10.8 = 7.6 bpm, most of a zone.
Resting heart rate matters less. The Karvonen target equals resting rate × (1 − intensity) + maximum × intensity, so at 70 % each beat of error in the resting rate moves the target by 0.3 bpm. For the woman above, a resting rate of 52 instead of 62 bpm lowers her 70 % target from 137.25 to 134.25 bpm. Count your pulse for a full minute before getting up, on several mornings, and use a typical value rather than the lowest.
Two things make the zones more reliable:
WHO advises all adults to do 150 to 300 minutes of moderate-intensity or 75 to 150 minutes of vigorous-intensity aerobic activity a week, or an equivalent mix (WHO 2020 guidelines). The NHS and the ACSM position stand set the same floor of 150 moderate or 75 vigorous minutes.
The American Heart Association puts moderate activity at about 50–70 % of maximum heart rate and vigorous activity at about 70–85 %. On the percent-of-maximum setting, zones 1 and 2 are moderate, and zone 3 plus the lower half of zone 4 are vigorous. For the woman above that is 85 to 119 bpm for moderate and 119 to 144 bpm for vigorous minutes.
Zone names are not standardised. The calculator follows Polar's five 10-point bands, where zone 2 is "light". In 2025 the ACSM and Exercise and Sport Science Australia proposed five common labels, very low, low, moderate, high and very high, because inconsistent intensity terms were hampering research and the uptake of guidelines (Med Sci Sports Exerc, 2025). Before copying a training plan's "zone 2" into the calculator, check which percentages and which method the plan uses.
The same two heart rates feed other estimates. The VO2 max calculator turns maximum and resting heart rate into an aerobic fitness estimate with Uth's ratio, the calories burned calculator converts time at an activity into energy, and the running pace calculator turns a target race time into a pace per kilometre or mile.
Checked against: Python 3.8 decimal: 208 − 0.7·40 = 180; (180 − 60)·0.70 + 60 = 144
Checked against: Python 3.8 decimal: 220 − 30 = 190; 190 × 0.85 = 161.5; 208 − 21 = 187
Checked against: Python 3.8 decimal: 208 − 0.7·100 = 138; 220 − 100 = 120
Checked against: Python 3.8 decimal: 206 − 0.88·55 = 157.6; (157.6 − 62)·0.70 + 62 = 128.92
The usual estimate is 220 minus age, which gives 180 bpm at 40. Tanaka and colleagues (2001) pooled 351 studies with 18,712 people and found that 208 − 0.7 × age fits better, especially in older adults: at 60 it gives 166 bpm against 160 bpm for 220 − age. Both predict a group average, so only a supervised maximal exercise test gives an individual value.
Target heart rate = (maximum − resting) × intensity + resting. The difference between maximum and resting rate is the heart-rate reserve. For a 40-year-old with a 180 bpm maximum and a resting rate of 60 bpm, 70 % intensity is 120 × 0.7 + 60 = 144 bpm. Karvonen, Kentala and Mustala described the method in 1957; at the same percentage it gives a higher target than a plain percent of maximum (126 bpm here).
In the five-zone split used by Polar and many sports watches, zone 2 is 60–70 % of maximum heart rate, or of heart-rate reserve with the Karvonen method. For a 40-year-old with a 180 bpm maximum and a 60 bpm resting rate, that is 132 to 144 bpm by Karvonen, or 108 to 126 bpm as a percent of maximum. Other brands and coaches define zones differently, so the same label can mean different numbers.
For adults, 60 to 100 beats per minute is the range usually given as normal, for example by the American Heart Association, and well-trained endurance athletes often sit below 60. Resting rate matters here because the Karvonen method adds it back: at a 180 bpm maximum, 70 % intensity is 138 bpm with a resting rate of 40 bpm and 150 bpm with 80 bpm.
Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 5 worked examples whose answers come from independent sources; for example, “Age 40, Tanaka, Karvonen at 70 %” is checked against Python 3.8 decimal: 208 − 0.7·40 = 180; (180 − 60)·0.70 + 60 = 144.
Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1):153–156; Gulati M, Shaw LJ, Thisted RA et al. Heart rate response to exercise stress testing in asymptomatic women: the St. James Women Take Heart Project. Circulation 2010;122(2):130–137; Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn 1957;35(3):307–315; Fox SM, Naughton JP, Haskell WL. Physical activity and the prevention of coronary heart disease. Ann Clin Res 1971;3:404–432; Polar — What are heart rate zones?.
For information only, not medical advice. These formulas describe populations, not you; talk to a clinician before acting on a result.
5 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.
VO2 max from the Cooper 12-minute run, the Rockport 1-mile walk or the resting heart-rate ratio, rated against Cooper Institute norms for age and sex.
Running pace per km or mile from distance and time, or finish time or distance from pace, with even splits and Riegel race predictions.
Calories burned by an activity from its MET value in the Compendium of Physical Activities, your body weight and the time spent.
Blood pressure category (AHA/ACC) for a systolic/diastolic reading, from normal to stage 2 and severe hypertension, with pulse pressure and MAP.
One-rep max (1RM) from a set of reps with the Epley, Brzycki, Lombardi and O'Conner equations, plus training loads from 50 % to 100 %.
Cycling power-to-weight (W/kg), speed and pace, or swimming pace per 100 m and 100 yd with your SWOLF score.
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