The most widely used formula for estimating maximum heart rate is simple: subtract your age from 220. A 40-year-old, for example, would have an estimated max heart rate of 180 beats per minute (bpm). This number serves as the ceiling for setting your exercise intensity zones, but it comes with a margin of error worth understanding.
The Two Main Formulas
The classic formula, 220 minus your age, has been the standard for decades and is still referenced by the American Heart Association. It’s easy to remember and good enough for most people starting an exercise routine. But it carries a standard deviation of 10 to 12 bpm, meaning your true max heart rate could be that much higher or lower than the estimate. For a 50-year-old, the formula predicts 170 bpm, but the actual number could fall anywhere from 158 to 182.
A more accurate alternative is the Tanaka formula: 208 minus 0.7 times your age. For the same 50-year-old, this gives 173 bpm. In a study comparing common prediction equations, the Tanaka formula had a slightly lower error rate than the classic 220-minus-age approach. Neither is perfect, but Tanaka tends to be more accurate for older adults, where the classic formula increasingly underestimates true max heart rate.
A Formula Designed for Women
Standard formulas were developed primarily from data on men, and they don’t always fit women well. A formula created specifically from female exercise data uses a different equation: 206 minus 0.88 times your age. For a 50-year-old woman, this gives 162 bpm compared to 170 from the classic formula.
When researchers applied the traditional 220-minus-age formula to women, only about 50% reached the predicted max heart rate during treadmill testing. Using the women-specific formula, that number jumped to nearly 70%. The gap was most noticeable in older women, where the standard formula consistently overestimated what their hearts could actually do. If you’re a woman using heart rate to guide your training, this formula gives you a more realistic starting point.
How to Use Max Heart Rate for Training Zones
Once you have your estimated max, you can set intensity targets. The American Heart Association and Mayo Clinic define two main zones:
- Moderate intensity: 50% to 70% of your max heart rate. This is the zone for brisk walking, easy cycling, or a casual swim.
- Vigorous intensity: 70% to 85% of your max heart rate. This covers running, fast cycling, competitive sports, and interval training.
For a 35-year-old with an estimated max of 185 bpm, moderate exercise would mean keeping your heart rate between about 93 and 130 bpm, while vigorous exercise falls between 130 and 157 bpm. If you’re new to exercise, start at the lower end of the moderate range and build up gradually.
Heart Rate Reserve: A More Personalized Method
A flat percentage of max heart rate ignores one important variable: your resting heart rate. Someone with a resting heart rate of 55 bpm is in a very different place physiologically than someone resting at 80 bpm, even if they’re the same age. The Karvonen method accounts for this by using something called heart rate reserve, which is simply your max heart rate minus your resting heart rate.
Here’s how it works in practice. Say you’re 40 years old with a resting heart rate of 65 bpm. Your estimated max is 180. Your heart rate reserve is 180 minus 65, which equals 115. To find a target heart rate for moderate exercise at 60% intensity, multiply 115 by 0.60 to get 69, then add your resting heart rate back: 69 plus 65 equals 134 bpm. This is your personalized target. For 80% intensity, the math gives you 157 bpm.
This method is used in cardiac rehabilitation programs, where patients typically aim for 60% to 80% of heart rate reserve plus resting heart rate. It’s equally useful for healthy exercisers who want training zones that reflect their actual fitness level rather than just their age.
Why Age Matters More Than Fitness
A common assumption is that fit people have higher maximum heart rates. They don’t. Research has shown that the decline in max heart rate with age is independent of sex, habitual physical activity, and other lifestyle factors. It’s a non-modifiable consequence of aging, driven by changes in how the heart’s electrical system responds to adrenaline-like signals.
What fitness does change is your resting heart rate. A well-trained heart pumps more blood per beat, so it doesn’t need to beat as fast at rest. This is why heart rate reserve is a more useful metric for fit individuals. Two 45-year-olds might share the same max heart rate, but the one with a resting heart rate of 52 has a much larger reserve to work with than the one resting at 78.
When Medications Change the Math
Beta-blockers, commonly prescribed for high blood pressure and heart conditions, lower both resting and exercise heart rates. They’re specifically designed to keep heart rate from climbing too high, which means standard formulas won’t apply. One approach suggested by Harvard Health is to reduce your target heart rate by the same amount the medication has lowered your resting rate, typically around 10 bpm. But beta-blockers also blunt the heart rate’s ability to rise during exercise, so even this adjustment may not fully capture the limitation.
If you take any heart rate-affecting medication, percentage-based targets from a formula won’t be reliable. The talk test (can you speak in full sentences?) or a perceived exertion scale may be better guides for intensity in this situation.
Getting Your True Max Heart Rate Measured
Every formula is an estimate. The only way to know your actual maximum heart rate is through a graded exercise test, sometimes called a stress test. In a clinical setting, you exercise on a treadmill or stationary bike while the workload increases in stages. The test continues until you reach your limit or until the monitoring shows a reason to stop.
Clinical guidelines consider a test adequate when you reach at least 85% of your predicted max heart rate. Failing to reach that threshold, or being unable to exercise for more than six minutes on the standard treadmill protocol, is itself a meaningful health indicator. These tests are typically ordered for people with suspected heart disease rather than for exercise planning, but some sports medicine clinics and performance labs offer them for athletes who want precise training data.
A simpler (though less precise) option is a field test: after a thorough warmup, run or cycle at maximum sustainable effort for three to four minutes, recover briefly, then repeat. The highest heart rate you hit during those intervals is a reasonable approximation of your true max. A chest strap heart rate monitor gives the most reliable reading for this kind of test.