Heart Rate Zone Calculator
Estimate your maximum heart rate and pinpoint target heart rate zones for any training intensity. Use it when designing a structured workout plan or dialing in effort levels for cardio sessions.
About this calculator
Maximum heart rate (MHR) is most commonly estimated as 220 − age, a formula derived from large population studies. Training target heart rate is then calculated as a fraction of that maximum. The simpler method multiplies MHR directly by the desired intensity: Target HR = round((220 − age) × intensity). The more precise Karvonen method incorporates your resting heart rate (HRrest) to use heart rate reserve (HRR): Target HR = round(((220 − age − HRrest) × intensity) + HRrest). Because HRR reflects actual cardiovascular fitness, Karvonen targets scale with individual conditioning — a runner with a 45 bpm resting HR gets different zone boundaries than a sedentary person of the same age. Both methods are widely used; the Karvonen formula is preferred when accuracy matters and resting HR is reliably measured.
How to use
Suppose you are 40 years old, your resting HR is 55 bpm, you choose the Karvonen method, and you want the target HR for 80% intensity (Zone 4). Step 1 – Estimate MHR: 220 − 40 = 180 bpm. Step 2 – Calculate HRR: 180 − 55 = 125 bpm. Step 3 – Apply Karvonen: (125 × 0.80) + 55 = 100 + 55 = 155 bpm. Using the simple method: 180 × 0.80 = 144 bpm. The Karvonen result (155 bpm) is higher because it accounts for your low resting HR, reflecting a higher actual fitness-adjusted threshold for Zone 4 effort.
Frequently asked questions
How accurate is the 220 minus age formula for estimating maximum heart rate?
The 220 − age formula is a population average with a standard deviation of roughly ±10–12 bpm, meaning your actual MHR could easily be 10 beats higher or lower than the estimate. It tends to overestimate MHR in older adults and underestimate it in very fit younger athletes. Alternative formulas such as Tanaka (208 − 0.7 × age) or Gelish (207 − 0.7 × age) have been shown to be more accurate across age groups. The most accurate method is a supervised maximal exercise test (graded treadmill or cycle ergometer test), but the formula is sufficient for general fitness training purposes.
What is heart rate reserve and why does the Karvonen method use it?
Heart rate reserve (HRR) is the range between your resting heart rate and your maximum heart rate: HRR = MHR − HRrest. A larger HRR generally indicates better cardiovascular fitness. The Karvonen method calculates target zones as a percentage of HRR added back to the resting HR, which means two people with identical maximum heart rates but different resting rates will have different training zone targets. This is physiologically meaningful because the resting HR reflects stroke volume and cardiac efficiency — a trained heart pumps more blood per beat, lowering resting HR and widening the usable training range.
When should I use the Karvonen method instead of the simple percentage method for heart rate training?
Use the Karvonen method when you have a reliably measured resting heart rate and are following a structured training plan where precision matters — for example, preparing for a marathon or triathlon and targeting specific aerobic versus anaerobic adaptations. The simple percentage method is fine for general fitness, casual gym cardio, or when you do not know your resting HR. If your resting HR is above 70 bpm (typical of sedentary individuals), the two methods produce similar results. If your resting HR is below 55 bpm, Karvonen will assign noticeably higher absolute zone boundaries, which better reflects your actual aerobic capacity.