The zone at a glance, age 35, resting 60
Maximum (220 − age)
185bpm
220 − 35. An estimate, not a measurement.
Zone as 80 to 90% of maximum
148 to 167bpm
Percent of maximum scale.
Zone as 80 to 90% of reserve
160 to 173bpm
Reserve is 125 bpm. Same percentages, different scale.
Average VT2 for the same maximum
168 to 177bpm
Lab average across six groups, applied to this maximum.
Key Takeaways
- Anaerobic heart rate has no single research definition. Polar calls zone 4 (80 to 90% of maximum) and zone 5 its anaerobic training zones[3]. WHOOP defines its anaerobic zone as 80 to 90% of heart rate reserve[5].
- The two scales give different beats. At maximum 185 and resting 60, the zone is 148 to 167 by maximum and 160 to 173 by reserve. An ACSM journal article says the two methods are not necessarily equivalent[7].
- A percent band is not the anaerobic threshold. In a lab study the average heart rate at the second ventilatory threshold was 90.6 to 95.6% of measured maximum across six groups, above the 90% top of the band[1].
- In 20 young women, any intensity from 75 to 90% of maximum put between 1 and 14 of them above their own threshold[2]. The authors say heart rate can still be used to stay above or below the threshold, but only once your own threshold heart rate has been measured.
- Your maximum is the weak link. Age equations have a standard error of 7 to 11 beats[11], which is the size of a typical miss. A zone built on one inherits that error.
- Beta blockers blunt the heart rate response, so you may never reach a standard target[20]. If you take medicine for your heart or blood pressure, ask your doctor for a target.
How the Zone Is Calculated, With Worked Examples
Multiply your maximum heart rate by 80% and 90%, or apply those percentages to your heart rate reserve.
The calculator uses a five-zone convention in which zone 4 runs from 80 to 90% of the base and zone 5 from 90 to 100%. Polar's guide gives these percentages of maximum heart rate for its anaerobic training zones[3]. WHOOP applies 80 to 90% to heart rate reserve[5].
Percent of maximum: zone = percent × maximum
Percent of reserve: zone = resting + percent × (maximum − resting)
Worked example: age 35, resting 60, percent of maximum
Maximum (220 − age) = 220 − 35 = 185 bpm
Zone low = 80% × 185 = 148 bpm
Zone high = 90% × 185 = 166.5, rounded to 167 bpm
Worked example: age 35, resting 60, percent of reserve
Maximum (220 − age) = 220 − 35 = 185 bpm
Reserve = 185 − 60 = 125 bpm
Zone low = 60 + 80% × 125 = 160 bpm
Zone high = 60 + 90% × 125 = 172.5, rounded to 173 bpm
Two vendor examples run through the same arithmetic. Results are rounded to the nearest beat, halves up.
| Source | Maximum | Resting | Scale | Source prints | This calculator |
|---|---|---|---|---|---|
| WHOOP | 200 | 50 | Reserve | 170 to 185 | 170 to 185 |
| WHOOP | 200 | 50 | Maximum | 160 to 180 | 160 to 180 |
| Polar V800 manual, age 30 | 190 | Not used | Maximum | 152 to 172 | 152 to 171 |
WHOOP is cited from its article[5] and Polar from its manual[4]. For the same 90% edge, Polar's table prints 172 at the top of zone 4 and 171 at the bottom of zone 5, and 90% of 190 is 171. A printed zone can differ from the arithmetic by one beat.
Percent of maximum from a pulse
heart rate ÷ maximum × 100
The zone formula solved for the percentage. Plain algebra, used by the pulse check.
Percent of reserve from a pulse
(heart rate − resting) ÷ reserve × 100
The reserve formula solved for the percentage.
Beats in 10 seconds
beats per minute ÷ 6
Arithmetic, for a quick count at the wrist.
Percent of Maximum or Percent of Reserve
The same percentages land on different beats, and the reserve version is always higher.
Reserve starts from your resting rate, so the gap to the percent-of-maximum zone is resting × (1 − percent). That is 20% of your resting rate at the 80% edge and 10% at the 90% edge. At resting 60 it is 12 beats at the bottom and 6 at the top.
The ACSM position stand says it cannot be assumed that one method of setting intensity gives the same result as another[6]. An ACSM journal article repeats that the methods are not necessarily equivalent, and adds that reserve has been suggested as potentially preferable[7].
None of the sources here tests which scale gives a better anaerobic target. Choose one and compare any watch against the same scale.
How Polar, WHOOP and ACSM Define the Zone
Each source draws the line in a different place, so one person gets several answers.
Polar and WHOOP are manufacturer guidance, not studies[3][5]. ACSM's classes come from a position stand table and describe intensity, not a threshold[6]. The table uses maximum 185 and resting 60.
| Definition | Type | Scale | Percent | bpm |
|---|---|---|---|---|
| Polar zone 4, hard | Manufacturer | Maximum | 80 to 90% | 148 to 167 |
| Polar zone 5, maximum | Manufacturer | Maximum | 90 to 100% | 167 to 185 |
| WHOOP zone 4, anaerobic | Manufacturer | Reserve | 80 to 90% | 160 to 173 |
| WHOOP zone 5, maximum | Manufacturer | Reserve | 90 to 100% | 173 to 185 |
| ACSM vigorous | Position stand | Maximum | 77 to 95% | 142 to 176 |
| ACSM vigorous | Position stand | Reserve | 60 to 89% | 135 to 171 |
| ACSM near maximal | Position stand | Maximum | 96% and above | 178 and above |
| ACSM near maximal | Position stand | Reserve | 90% and above | 173 and above |
The 80 to 90% band sits inside ACSM's vigorous range for percent of maximum (77 to 95%). On the reserve scale its 90% top edge reaches ACSM's near maximal class[6].
ACSM pairs vigorous effort with an RPE of 14 to 17 on the 6 to 20 scale, a check that needs no device. The RPE Calculator covers it.
What Lab Tests Show About the 80 to 90% Band
Measured thresholds sit higher than the band for most groups, and they vary with training status.
Benítez-Muñoz and colleagues found the first and second ventilatory thresholds (VT1 and VT2) on a treadmill ramp test in adults tested from 2003 to 2023, with mean ages of 36.8 years in men and 33.9 in women[1]. They grouped people by training status.
| Group | n | VT1, % of max | VT2, % of max | VT1 bpm | VT2 bpm |
|---|---|---|---|---|---|
| Men, low | 212 | 74.6 | 90.6 | 133 | 162 |
| Men, medium | 436 | 78.6 | 93.5 | 143 | 170 |
| Men, high | 317 | 80.8 | 94.6 | 150 | 175 |
| Women, low | 53 | 77.9 | 93.1 | 138 | 164 |
| Women, medium | 160 | 81 | 94.6 | 145 | 169 |
| Women, high | 80 | 82.9 | 95.6 | 152 | 176 |
Average VT2 was 90.6 to 95.6% of maximum heart rate, so every group averaged above the 90% top of the band. Average VT1 was 74.6 to 82.9%, so the 80% bottom edge falls inside that range[1].
The percentages differed by training status in both sexes. In men both rose with each step up in status, and in women both were higher in the medium and high groups than in the low group. Maximum heart rate itself did not differ by status[1].
The authors conclude that, because the percentage at which thresholds occur is higher in people with a higher training status, "the common strategy consisting of establishing exercise intensity as a fixed percentage of maximum might not be effective to match intensity across individuals with different training status"[1].
What this means for the zone
Using the example maximum of 185, average VT2 comes to 168 to 177 bpm. The top of the zone, 167, is 1 to 10 bpm below that average. The percentages in the study are of measured maximum, so an estimated maximum adds its own error on top.
A 1983 study points the same way. Dwyer and Bybee tested 20 young women on a cycle ergometer. Heart rate at the ventilatory threshold averaged 158.4 beats a minute, 86.3% of maximum[2].
At any intensity from 75 to 90% of maximum, between 1 and 14 of the 20 women were above their own threshold. The authors write that heart rate cannot identify the threshold, but can be used to regulate intensity above or below it if the threshold heart rate is assessed for each person[2].
Your Maximum Heart Rate Sets the Zone
Every edge of the zone is a percentage of a maximum, so an error in the maximum moves the whole zone.
220 minus age is the default because the American Heart Association chart uses it[21]. Pick another equation or enter a measured maximum and every number follows. ACSM's guidelines prefer a directly measured maximum and accept an estimate when that is not feasible[7].
| Equation | Built from | Maximum | Zone |
|---|---|---|---|
| 220 − age | Not developed from original research. Age-based estimates have a standard error of 7 to 11 beats[11] | 185 | 148 to 167 |
| Tanaka (2001)208 − 0.7 × age | Review of 351 studies (18,712 people), checked in 514 healthy adults[12] | 184 | 147 to 166 |
| Gellish (2007)207 − 0.7 × age | 132 people with 908 maximal tests over 25 years[13] | 183 | 146 to 165 |
| HUNT (2013)211 − 0.64 × age | 3,320 healthy adults, standard error 10.8 beats[14] | 189 | 151 to 170 |
| Gulati (2010)206 − 0.88 × age | 5,437 asymptomatic women[15] | 175 | 140 to 158 |
| Inbar (1994)205.8 − 0.685 × age | 1,424 men aged 20 to 70[16] | 182 | 146 to 164 |
Six published equations for maximum heart rate, with the zone at age 35, percent of maximum scale
At age 35 the six equations give maximums from 175 to 189, a spread of 14 beats. If the true maximum is 11 lower than 185, the zone is 139 to 157. If it is 11 higher, the zone is 157 to 176[11].
Shookster and colleagues compared 9 equations against 99 graded treadmill tests and found poor agreement for all of them. They say the Fox equation may be the best option for a general population[17].
The same authors advise using data from a graded exercise test when it is available[17]. Mayo Clinic says your maximum can be higher or lower than the formula figure, sometimes by as much as 15 to 20 beats[19].
If you know your real maximum
Choose "I know my measured maximum" and enter it. The sensitivity note then disappears, because the zone does not rest on an estimate.
Why Heart Rate Lags and Drifts
Heart rate follows effort with a delay, and conditions move it.
Polar's manual says heart rate takes about 3 to 5 minutes to adjust when you move from zone 1 to zone 3[4]. That is manufacturer guidance for its own zones.
A review of heart rate monitoring reports that heart rate increases steadily during exercise in most studies, and that dehydration and ambient temperature can have a profound effect on the relationship between heart rate and oxygen uptake[18]. A zone is therefore a guide to effort, not a fixed measure of it.
Medication, Heart Conditions and Age
On a beta blocker, a predicted maximum can send you to the wrong zone.
Beta blockers blunt the heart rate response. Mayo Clinic says you might never reach your target heart rate on one, however hard you exercise[20]. The American Heart Association says some drugs and medicines lower maximum heart rate and the target zone[21].
If you take medicine for your heart or blood pressure, or have a heart condition, ask your doctor for a target instead of using these numbers.
The lab data come from adults with mean ages of 36.8 and 33.9 years[1]. The calculator adds a note outside ages 18 to 56, two standard deviations around those means.
Zone 4 and Zone 5 by Age
These rows show the convention at each age. They are not threshold heart rates.
The table uses 220 minus age because the American Heart Association chart does[21], and percent of maximum so no resting rate is needed. A measured maximum or another equation changes every row.
| Age | Maximum | Zone 4 | Zone 5 |
|---|---|---|---|
| 20 | 200 | 160 to 180 | 180 to 200 |
| 25 | 195 | 156 to 176 | 176 to 195 |
| 30 | 190 | 152 to 171 | 171 to 190 |
| 35 | 185 | 148 to 167 | 167 to 185 |
| 40 | 180 | 144 to 162 | 162 to 180 |
| 45 | 175 | 140 to 158 | 158 to 175 |
| 50 | 170 | 136 to 153 | 153 to 170 |
| 55 | 165 | 132 to 149 | 149 to 165 |
| 60 | 160 | 128 to 144 | 144 to 160 |
| 65 | 155 | 124 to 140 | 140 to 155 |
| 70 | 150 | 120 to 135 | 135 to 150 |
| 75 | 145 | 116 to 131 | 131 to 145 |
| 80 | 140 | 112 to 126 | 126 to 140 |
When You Need a Tested Number
A threshold heart rate has to be measured, and even then the name covers several markers.
Ghosh lists lactate threshold, ventilatory anaerobic threshold, onset of blood lactate accumulation, heart rate deflection point and maximal lactate steady state among the terms scientists use for this transition[10]. Walsh and Banister describe the anaerobic threshold as consisting of a lactate threshold and a ventilatory threshold[9].
Faude and colleagues describe an intense and ongoing debate about the terminology and physiological background of lactate thresholds[8]. A zone from a percentage cannot settle which one you are training near.
For a threshold estimate from a field test, with the lab spread shown, use the Anaerobic Threshold Calculator. For an easy aerobic range see the Zone 2 Heart Rate Calculator. All five zones side by side are in Target Heart Rate Zones Calculator, and the reserve method alone is in the Karvonen Heart Rate Calculator.
To plan sessions around an intensity, use the Training Intensity Calculator.
Not Covered
Training doses
No study here gives a weekly dose for the 80 to 90% band. Manufacturer guidance exists: Polar advises a maximum of two to three zone 5 sessions a week[3], and WHOOP says most athletes can handle 1 to 3 anaerobic sessions a week, depending on recovery[5]. ACSM's minimum for vigorous exercise is at least 20 minutes on at least 3 days a week[6]. This calculator does not prescribe a dose.
Fitness-level percentages
No source gives fitness-level percentages for this band. The lab table shows the measured spread by training status instead.
Threshold heart rate by age
No source here gives a threshold heart rate by age. The by-age table shows the convention, not a threshold.
Blood lactate
Only ventilatory thresholds are shown. Blood lactate values are not calculated.
Sex in the convention
The percent bands have no sex input. The lab table is split by sex because the study reported the groups separately.
Frequently Asked Questions
Sources & References
- Differences in the ventilatory thresholds in treadmill according to training status in 971 males and 301 females: a cross-sectional study. Benítez-Muñoz JA, Benito PJ, Guisado-Cuadrado I, Cupeiro R, Peinado AB. European Journal of Applied Physiology 125:499-510 (2025)
- Heart rate indices of the anaerobic threshold. Dwyer J, Bybee R. Medicine & Science in Sports & Exercise 15(1):72-76 (the abstract is on the publisher page; the PubMed record has none) (1983)
- Anaerobic Training | Heart Rate Zones 4-5 (manufacturer guidance). Polar. polar.com guide, no date shown on the page
- V800 User Manual: Heart Rate Zones (manufacturer guidance). Polar Electro. support.polar.com
- Anaerobic Heart Rate Zone: Benefits and Exercises (manufacturer guidance, 15 May 2026). WHOOP (Meserve C). whoop.com The Locker (2026)
- American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise (Table 5). Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, et al.. Medicine & Science in Sports & Exercise 43(7):1334-1359 (Table 5 is in the full text; the abstract gives the vigorous exercise minimum) (2011)
- Estimating Maximal Heart Rate. Bushman BA. ACSM's Health & Fitness Journal 27(6):5-8 (2023)
- Lactate threshold concepts: how valid are they?. Faude O, Kindermann W, Meyer T. Sports Medicine 39(6):469-490 (2009)
- Possible mechanisms of the anaerobic threshold. A review. Walsh ML, Banister EW. Sports Medicine 5(5):269-302 (1988)
- Anaerobic threshold: its concept and role in endurance sport. Ghosh AK. Malaysian Journal of Medical Sciences 11(1):24-36 (2004)
- The surprising history of the "HRmax=220-age" equation. Robergs RA, Landwehr R. Journal of Exercise Physiology online (2002)
- Age-predicted maximal heart rate revisited. Tanaka H, Monahan KD, Seals DR. Journal of the American College of Cardiology (2001)
- Longitudinal modeling of the relationship between age and maximal heart rate. Gellish RL, Goslin BR, Olson RE, McDonald A, Russi GD, Moudgil VK. Medicine & Science in Sports & Exercise (2007)
- Age-predicted maximal heart rate in healthy subjects: The HUNT fitness study. Nes BM, Janszky I, Wisløff U, Støylen A, Karlsen T. Scandinavian Journal of Medicine & Science in Sports (2013)
- Heart rate response to exercise stress testing in asymptomatic women: the St. James Women Take Heart Project. Gulati M, Shaw LJ, Thisted RA, Black HR, Bairey Merz CN, Arnsdorf MF. Circulation (2010)
- Normal cardiopulmonary responses during incremental exercise in 20- to 70-yr-old men. Inbar O, Oren A, Scheinowitz M, Rotstein A, Dlin R, Casaburi R. Medicine & Science in Sports & Exercise (the abstract gives the slope only; the intercept is confirmed through Robergs and Landwehr) (1994)
- Accuracy of Commonly Used Age-Predicted Maximal Heart Rate Equations. Shookster D, Lindsey B, Cortes N, Martin JR. International Journal of Exercise Science (2020)
- Heart rate monitoring: applications and limitations. Achten J, Jeukendrup AE. Sports Medicine 33(7):517-538 (abstract) (2003)
- Exercise intensity: How to measure it. Mayo Clinic (2023)
- Beta blockers: How do they affect exercise?. Mayo Clinic (2023)
- Target Heart Rates Chart (reviewed August 2024). American Heart Association (2024)
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Disclaimer: This calculator provides estimates based on published formulas and population averages. Results are for informational and personal logging purposes only. Individual results may vary.