Why does the calculator use 220 minus age?

The Fox formula (220 − age) is the most widely cited age-based MHR estimate, introduced in 1971 and adopted by clinical and fitness organizations for decades. While newer equations exist, the Fox formula remains the default reference in many guidelines and educational materials.

How accurate is this estimate for my actual maximum heart rate?

Population studies show a standard deviation of ±10–12 bpm around the Fox prediction. Individual genetics, training status, and sport-specific adaptations can shift actual MHR by 20+ bpm. Laboratory graded exercise testing or a field-based max test provides a more precise personal value.

What do the five zones represent physiologically?

Z1 Recovery facilitates active rest with minimal lactate accumulation. Z2 Endurance builds mitochondrial density and aerobic capacity. Z3 Tempo develops lactate clearance at moderate intensity. Z4 Threshold trains near the lactate inflection point. Z5 VO2max targets maximal oxygen uptake and anaerobic contribution.

Can I use these zones if I take heart-rate-lowering medication?

Beta-blockers, calcium-channel blockers, and other cardiac medications alter heart-rate response to exercise, rendering age-predicted zones unreliable. A physician-supervised exercise test with medication on board is necessary to establish safe and effective training ranges in these cases.

How do percentage-of-MHR zones compare to lactate or threshold-based models?

Percentage-of-MHR zones are simple and require only age, but they do not account for individual fitness or lactate kinetics. Lactate-threshold or functional-threshold-based models anchor zones to measured physiological breakpoints, offering greater precision for trained athletes but requiring lab or field testing.

Heart Rate Zones

Heart Rate Zones (% of Max)

Calculate five heart-rate training zones from age-based maximum heart rate using the Fox formula.

Last updated: 22 April 2026

What this tool does

This calculator estimates maximum heart rate using the Fox formula (220 − age) and divides that maximum into five training zones based on percentage ranges: Z1 Recovery (50–60%), Z2 Endurance (60–70%), Z3 Tempo (70–80%), Z4 Threshold (80–90%), and Z5 VO2max (90–100%). It requires only age as an input and outputs heart rate ranges in beats per minute for each zone. The Fox equation provides a population-average estimate; individual maximum heart rate can vary by ±10–12 bpm from the predicted value.

Inputs

Result

—

Formula Used

MHR = 220 - age, Z_{i} = [pct_{i}^{l o}, pct_{i}^{hi}] \times MHR

a

Age in years

Spotted something off? Let us know — we update calculators regularly.

How Heart Rate Zones (% of Max) works

This calculator divides cardiovascular effort into five training zones based on percentages of maximum heart rate (MHR). It estimates MHR using the Fox formula (220 − age), then calculates five ranges: Z1 Recovery (50–60%), Z2 Endurance (60–70%), Z3 Tempo (70–80%), Z4 Threshold (80–90%), and Z5 VO2max (90–100%). The primary result displays the Tempo zone (Z3), while all five zones appear in the breakdown. Each zone represents a distinct physiological state—Z1 promotes active recovery, Z2 builds aerobic base, Z3 develops lactate clearance, Z4 increases lactate threshold, and Z5 targets maximal oxygen uptake.

The formula

Maximum Heart Rate (MHR) = 220 − age. For each zone, lower bound = MHR × zone_min and upper bound = MHR × zone_max. Example: a 30-year-old has an estimated MHR of 190 bpm; Z3 Tempo = 190 × 0.70 to 190 × 0.80 = 133–152 bpm. The Fox formula originated in 1971 and remains the most widely recognized clinical estimate despite known individual variation of ±10–12 bpm standard deviation.

Where this method is most accurate

Age-based MHR estimates perform best as population averages for adults aged 20–65 with no cardiac conditions. The Fox formula tends to overestimate MHR in older adults and underestimate in younger populations. Alternative equations like Tanaka (208 − 0.7×age) or Nes/Gulati offer improved fit in specific cohorts but still carry population-level error. Individual MHR can differ from the predicted value by 20+ bpm due to genetics, fitness history, and sport-specific adaptation. Laboratory graded exercise testing or field-based max-effort protocols yield the most precise zone boundaries for individualized training prescription.

What this tool does not do

This calculator does not measure actual heart rate, diagnose cardiovascular conditions, or prescribe training plans. It estimates zones from an age-based formula; it does not account for medications (beta-blockers, calcium-channel blockers), altitude, heat stress, overtraining, or individual MHR variance. The tool does not determine appropriate session duration, frequency, or progression. Zone models vary by coaching philosophy—some systems use three zones, others seven; this tool implements the classical five-zone percentage-of-MHR model only.

Disclaimer

This tool is provided for educational and informational purposes only. It does not constitute medical advice, diagnosis, treatment, or professional training guidance. Consult a qualified healthcare provider before beginning any exercise program, especially if pre-existing cardiac, metabolic, or other medical conditions are present. Individual maximum heart rate and training zone responses vary widely; laboratory or field testing is recommended for precision. The calculator is not a substitute for individualized coaching or clinical evaluation.

Questions

Why does the calculator use 220 minus age?: The Fox formula (220 − age) is the most widely cited age-based MHR estimate, introduced in 1971 and adopted by clinical and fitness organizations for decades. While newer equations exist, the Fox formula remains the default reference in many guidelines and educational materials.
How accurate is this estimate for my actual maximum heart rate?: Population studies show a standard deviation of ±10–12 bpm around the Fox prediction. Individual genetics, training status, and sport-specific adaptations can shift actual MHR by 20+ bpm. Laboratory graded exercise testing or a field-based max test provides a more precise personal value.
What do the five zones represent physiologically?: Z1 Recovery facilitates active rest with minimal lactate accumulation. Z2 Endurance builds mitochondrial density and aerobic capacity. Z3 Tempo develops lactate clearance at moderate intensity. Z4 Threshold trains near the lactate inflection point. Z5 VO2max targets maximal oxygen uptake and anaerobic contribution.
Can I use these zones if I take heart-rate-lowering medication?: Beta-blockers, calcium-channel blockers, and other cardiac medications alter heart-rate response to exercise, rendering age-predicted zones unreliable. A physician-supervised exercise test with medication on board is necessary to establish safe and effective training ranges in these cases.
How do percentage-of-MHR zones compare to lactate or threshold-based models?: Percentage-of-MHR zones are simple and require only age, but they do not account for individual fitness or lactate kinetics. Lactate-threshold or functional-threshold-based models anchor zones to measured physiological breakpoints, offering greater precision for trained athletes but requiring lab or field testing.

Sources & Methodology

Estimates maximum heart rate using the Fox formula (MHR = 220 − age), then defines five zones as percentage ranges: Z1 Recovery 50–60%, Z2 Endurance 60–70%, Z3 Tempo 70–80%, Z4 Threshold 80–90%, Z5 VO2max 90–100% of MHR. Fox et al., 1971.

More in Heart Rate Zones

View all 6 →