Health & Medicine · Fitness · Cardio & Endurance
Target Heart Rate Calculator
Calculate your target heart rate zone for aerobic and anaerobic exercise based on age, resting heart rate, and desired intensity.
Calculator
Formula
THR is the target heart rate in beats per minute. HR_max is the maximum heart rate (220 minus age). HR_rest is the resting heart rate in beats per minute. %Intensity is the desired exercise intensity expressed as a decimal (e.g. 0.65 for 65%).
Source: Karvonen M, Kentala E, Mustala O. The effects of training on heart rate. Ann Med Exp Biol Fenn. 1957;35(3):307-315.
How it works
The Karvonen method begins by estimating your maximum heart rate (HR_max) using the formula HR_max = 220 − age. Your heart rate reserve (HRR) is then calculated as HR_max minus your resting heart rate. The target heart rate (THR) for a given intensity is: THR = (HRR × %Intensity) + Resting HR. This personalizes the target zone relative to your cardiovascular fitness baseline.
Unlike the simpler percentage-of-max-HR method, the Karvonen formula accounts for the fact that a well-trained athlete with a low resting heart rate has a wider HRR and therefore a different absolute training zone than a sedentary individual of the same age. This makes zones more physiologically meaningful and individually accurate.
The five standard training zones correspond to progressively higher physiological demands: Zone 1 (recovery and warm-up), Zone 2 (fat oxidation and aerobic base building), Zone 3 (aerobic endurance), Zone 4 (lactate threshold training), and Zone 5 (neuromuscular power and VO2 max). Structuring workouts across these zones is the foundation of periodized endurance training.
Worked example
Example: A 35-year-old runner with a resting heart rate of 58 bpm wants to train at 65–75% intensity.
Step 1 — Max HR: 220 − 35 = 185 bpm
Step 2 — HRR: 185 − 58 = 127 bpm
Step 3 — Lower THR (65%): (127 × 0.65) + 58 = 82.55 + 58 = 141 bpm
Step 4 — Upper THR (75%): (127 × 0.75) + 58 = 95.25 + 58 = 153 bpm
The target training zone is approximately 141–153 bpm, which falls in the Zone 3 aerobic endurance range for this individual.
Limitations & notes
The formula 220 − age is a population-average estimate with a standard deviation of roughly ±10–12 bpm. Highly trained athletes or individuals with certain cardiac conditions may have significantly higher or lower actual maximums. For precision sport coaching or cardiac rehab, a medically supervised maximal exercise test (VO2 max test or Bruce protocol) should be used to determine true HR_max. The calculator also assumes a healthy, non-medicated individual; beta-blockers and other chronotropic medications substantially alter heart rate responses and invalidate these estimates.
Frequently asked questions
What is a normal resting heart rate?
For most adults, a normal resting heart rate is between 60 and 100 bpm. Physically fit individuals, especially endurance athletes, often have resting heart rates between 40 and 60 bpm. Measure yours first thing in the morning before getting out of bed for the most accurate reading.
Why does the Karvonen formula give different results than a simple percentage of max HR?
The simple method (e.g. 70% of 185 bpm = 130 bpm) ignores your resting heart rate baseline. The Karvonen method incorporates heart rate reserve — the range between rest and maximum — so it adjusts for individual fitness. A person with a resting HR of 45 bpm will have a higher Karvonen-based target than someone with 75 bpm at the same intensity level, reflecting their greater cardiovascular efficiency.
Which heart rate zone is best for fat burning?
Zone 2 (approximately 60–70% of HRR) is often called the 'fat-burning zone' because the body preferentially oxidizes fat for fuel at this moderate intensity. However, higher-intensity zones burn more total calories per unit time, which also contributes to fat loss. Zone 2 training is most effective for sustainable aerobic base building and metabolic efficiency over the long term.
Is the 220 − age formula accurate for everyone?
No. The 220 − age formula is a statistical average derived from population studies, and it carries a standard deviation of approximately ±10–12 bpm. It can substantially under- or overestimate maximum heart rate for any given individual, particularly older adults and highly trained athletes. For more accurate results, use a laboratory-measured or field-tested maximum heart rate, or apply alternative formulas such as Tanaka (208 − 0.7 × age), which was validated in a 2001 meta-analysis.
How does exercise affect my resting heart rate over time?
Regular aerobic training causes the heart to become more efficient, pumping more blood per beat (increased stroke volume). This adaptation lowers resting heart rate over months of consistent training. Elite endurance athletes can achieve resting heart rates below 40 bpm. A lower resting heart rate expands your HRR, meaning your Karvonen-calculated training zones will shift to slightly higher absolute bpm values as your fitness improves.
Can I use this calculator if I take heart-rate-lowering medications?
No. Beta-blockers, calcium channel blockers, and certain other medications significantly suppress maximum and resting heart rates, making age-predicted formulas unreliable. If you are on such medications, consult your physician or use perceived exertion scales (e.g. the Borg RPE scale) alongside heart rate monitoring to guide exercise intensity.
Last updated: 2025-01-30 · Formula verified against primary sources.