What Is the Karvonen Formula?
The Karvonen formula is the standard way to calculate personalized heart rate training zones from 2 numbers you already have: your max heart rate and your resting heart rate. Most heart rate zone charts skip the second number entirely, handing everyone the same range based on age alone. Karvonen doesn't. It builds your zones around heart rate reserve, the gap between how fast your heart beats at rest and how fast it can beat at full effort, so 2 people the same age with different fitness levels end up with different, more accurate zones.
Target HR = Resting HR + (Intensity% × HRR)
The method is also called the Heart Rate Reserve method, since HRR is what does the work. For the math behind HRR on its own, see our dedicated heart rate reserve guide.
Where the Formula Comes From
Finnish physiologist Martti Karvonen introduced the formula in a 1957 study that tracked how heart rate responded to different training intensities. The research identified roughly 60% of heart rate reserve as the threshold where a training effect reliably showed up, a finding that still anchors the lower end of most zone systems used today, including the 5-zone breakdown on this site.
The formula caught on because it solved a real problem. A percentage-of-max-heart-rate chart assigns the same zone to a marathoner and someone who hasn't exercised in years, as long as they're the same age. Karvonen's method doesn't.
Karvonen vs. Straight Percentage of Max Heart Rate
The difference between the 2 methods comes down to what each one measures. Straight percentage of max heart rate multiplies your estimated max heart rate by a percentage, full stop. Karvonen starts from your resting heart rate and works up from there, using it as a stand-in for cardiovascular fitness that age alone can't capture.
Max HR = 220 − 40 = 180 bpm
Straight %Max HR, Zone 2 (60–70%) = 108–126 bpm
Karvonen: HRR = 180 − 50 = 130 bpm → Zone 2 = 50 + (0.60–0.70 × 130) = 128–141 bpm
Max HR = 220 − 40 = 180 bpm
Straight %Max HR, Zone 2 (60–70%) = 108–126 bpm
Karvonen: HRR = 180 − 80 = 100 bpm → Zone 2 = 80 + (0.60–0.70 × 100) = 140–150 bpm
Same age, same estimated max heart rate, same 60 to 70% target, and the straight percentage method gives both people an identical zone: 108 to 126 bpm. Karvonen gives them different zones, because it's the only one of the 2 methods that factors in how each person's heart behaves at rest.
The distinction isn't just theoretical. Research comparing the 2 methods against directly measured oxygen consumption found that percent of heart rate reserve tracks percent of VO2 reserve more closely than percent of max heart rate does, particularly at lower and moderate intensities, which is exactly where the 2 methods diverge most.
How to Calculate Your Zones, Step by Step
- Find your max heart rate. 220 minus age is the default estimate. The Tanaka formula is more accurate for most adults, especially after 40.
- Find your resting heart rate. Check your pulse for 60 seconds first thing in the morning, before getting out of bed, or use the resting HR calculator to log it.
- Subtract to get heart rate reserve. HRR = Max HR − Resting HR.
- Pick an intensity percentage for the zone you want, such as 60 to 70% for Zone 2.
- Add it back to your resting heart rate. Target HR = Resting HR + (Intensity% × HRR).
- Repeat for each zone boundary you want to know, or let the calculator on the homepage do all 5 zones at once.
3 Worked Examples Across Different Ages
Here's the full calculation for Zone 2 (60 to 70% HRR) across 3 different ages and resting heart rates, all using 220 minus age for max heart rate to keep the comparison consistent.
Max HR = 220 − 25 = 195 bpm
HRR = 195 − 58 = 137 bpm
Zone 2 = 58 + (0.60–0.70 × 137) = 140–154 bpm
Max HR = 220 − 45 = 175 bpm
HRR = 175 − 68 = 107 bpm
Zone 2 = 68 + (0.60–0.70 × 107) = 132–143 bpm
Max HR = 220 − 65 = 155 bpm
HRR = 155 − 72 = 83 bpm
Zone 2 = 72 + (0.60–0.70 × 83) = 122–130 bpm
For the 65-year-old, it's worth using the Tanaka formula instead of 220 minus age, since the gap between the 2 widens with age. See our guide to target heart rate for seniors for that version of the calculation.
Why Your Max Heart Rate Estimate Still Matters
Karvonen fixes the resting heart rate half of the equation, but it doesn't fix the max heart rate half. If your max heart rate estimate is off, your zones shift too, no matter which formula fed it. 220 minus age has a documented margin of error of roughly ±10 to 12 bpm at the individual level, which is why formulas like Tanaka exist as more accurate alternatives, particularly as you get older. See our breakdown of the 220-minus-age formula's accuracy and limitations for the full picture.
The most accurate max heart rate you can use is one you've measured directly, during a race, a hard interval session, or a supervised test. Short of that, picking the formula that fits your age and using Karvonen to personalize the rest gets you closest.
Frequently Asked Questions
What is the Karvonen formula?
The Karvonen formula calculates a personalized target heart rate using heart rate reserve, the gap between your resting heart rate and your max heart rate, rather than a straight percentage of max heart rate alone. The formula is Target HR = Resting HR + (Intensity% × Heart Rate Reserve), where Heart Rate Reserve equals Max HR minus Resting HR.
Is the Karvonen formula more accurate than percentage of max heart rate?
Research comparing the 2 methods against measured oxygen consumption has found that percent of heart rate reserve tracks percent of VO2 reserve more closely than percent of max heart rate does, particularly at lower and moderate intensities. Karvonen also accounts for individual fitness through resting heart rate, which a straight percentage of max heart rate ignores entirely.
Where does the Karvonen formula come from?
Finnish physiologist Martti Karvonen introduced the formula in a 1957 study that tracked how heart rate responded to different training intensities, identifying roughly 60% of heart rate reserve as the threshold where a training effect reliably appeared.
How do I calculate my heart rate zones with the Karvonen formula?
Find your max heart rate and resting heart rate, subtract to get heart rate reserve, then add your resting heart rate back to a percentage of that reserve for each zone boundary. The free Karvonen calculator on this site does the math automatically once you enter your age and resting heart rate.
This article is for general informational purposes only and does not constitute medical advice. Consult a physician before starting or changing an exercise program, particularly if you have a chronic health condition or take medications that affect heart rate.