The most common way to estimate your maximum heart rate is to subtract your age from 220. A 40-year-old, for example, would get an estimated max of 180 beats per minute (bpm). This formula is simple and widely used, but it’s not especially precise. Several newer formulas improve accuracy, and understanding the differences can help you set smarter training zones.
The Standard Formula and Its Limits
The classic formula, known as the Fox formula, dates back to the 1970s and was developed from studies conducted primarily on men. It works like this:
- Fox formula: 220 minus your age
The American Heart Association still references this equation as a quick estimate, and it remains the default on most gym cardio machines. But every age-based formula carries a margin of error. The American College of Sports Medicine notes that all estimation equations have a standard error of 3 to 12 bpm, meaning your true maximum could be a full 12 beats higher or lower than the number you calculate. In younger populations, the Fox formula tends to overestimate. A study of adolescent female volleyball players found it overshot their actual measured max by an average of nearly 6 bpm.
More Accurate Alternatives
Researchers have developed formulas that perform better across broader age ranges. Two of the most validated options are:
- Tanaka formula: 208 minus (0.7 × your age)
- Gellish formula: 207 minus (0.7 × your age)
A large analysis published in PLOS ONE compared multiple formulas against directly measured maximum heart rates. The Tanaka and Gellish equations both produced the lowest average errors, each off by about 7.4 bpm on average. Both significantly outperformed the Fox formula in terms of absolute accuracy. That said, the Fox formula showed the most stable performance across different heart rate ranges, without a pattern of over- or underestimating at specific fitness levels.
For practical purposes, if you’re 50 years old, here’s how the numbers compare: the Fox formula gives you 170 bpm, while both the Tanaka and Gellish formulas give you 173 bpm. The gap widens at older ages and narrows for younger people.
A Different Formula for Women
The Fox formula was built on data from male subjects. Research from Northwestern Medicine led to a sex-specific equation for women:
- Gulati formula (women): 206 minus (88% of your age)
A 45-year-old woman using the standard formula would estimate her max at 175 bpm. The Gulati formula puts it at about 166 bpm, a meaningful difference when calculating training zones. Women have different physiological responses during exercise, including differences in exercise capacity, and this formula accounts for that. If you’re a woman relying on the 220-minus-age number, you may be training at a higher relative intensity than you realize.
How to Use Your Max for Training Zones
Once you have your estimated maximum heart rate, you can set target zones based on the intensity you’re aiming for. The American Heart Association defines two key ranges:
- Moderate intensity: 50% to 70% of your maximum heart rate
- Vigorous intensity: 70% to 85% of your maximum heart rate
To calculate these, multiply your estimated max by the percentage. A person with an estimated max of 180 bpm would aim for 90 to 126 bpm during moderate exercise (like brisk walking) and 126 to 153 bpm during vigorous exercise (like running or cycling hard). If your formula underestimates your true max by 10 beats, your zones will be slightly too low, meaning you could push a bit harder. If it overestimates, you might be working closer to your actual ceiling than you think.
A heart rate monitor (chest strap or optical wrist sensor) makes it easy to check where you fall during a workout. Chest straps are more accurate during high-intensity or interval training, while wrist-based monitors work well enough for steady-state cardio.
When Formulas Won’t Work
Certain medications fundamentally change how your heart responds to exercise. Beta-blockers, commonly prescribed for high blood pressure and heart conditions, slow the heart rate and can prevent it from climbing to its usual peak. There’s no simple correction factor to apply. If you take a beta-blocker or similar heart-rate-lowering medication, percentage-based zones won’t give you reliable guidance.
The alternative is a perceived exertion scale, such as the Borg Rating of Perceived Exertion. Instead of targeting a number on your watch, you rate how hard you feel you’re working on a scale from 6 (no effort) to 20 (absolute maximum). Moderate exercise typically falls around 12 to 14, where you’re breathing harder but can still hold a conversation. This approach bypasses heart rate entirely and works well for anyone whose heart rate response is blunted or unpredictable.
Altitude and Heat Change the Picture
Environmental conditions affect your heart rate during exercise in ways that can be counterintuitive. At high altitude, your heart rate runs higher at any given effort level because your body is compensating for lower oxygen. But your achievable maximum heart rate actually drops. Research published in Circulation found that at extreme altitude (around 5,260 meters, or 17,000 feet), this reduction is driven by nervous system changes. At 7,625 meters, maximum heart rate fell by 20% and exercise capacity dropped by 40% to 50%.
You don’t need to be mountaineering for altitude to matter. Even at ski-resort elevations of 2,500 to 3,000 meters, you’ll notice your heart rate is higher during a moderate hike than it would be at sea level, while your top-end feels harder to reach. Heat has a similar effect on submaximal heart rate: your heart works harder to cool you down, so the same jog that puts you at 140 bpm in cool weather might push you to 155 bpm on a hot day.
Finding Your Actual Maximum
If you want precision rather than an estimate, you need to measure your maximum heart rate directly. The gold standard is a graded exercise test, typically performed on a treadmill or stationary bike in a clinical or sports-performance setting. The intensity increases in stages until you physically can’t continue, and your peak heart rate is recorded.
A simpler field test involves warming up thoroughly, then running three to four hard intervals of 2 to 3 minutes each (like sprinting up a hill), with brief recovery between them. The highest heart rate you record on the last interval is a reasonable approximation of your max. This approach isn’t appropriate if you have a heart condition, haven’t exercised in a long time, or have risk factors that make all-out exertion unsafe.
For most people who exercise regularly and just want sensible training zones, a formula gets you close enough. Use the Tanaka formula (208 minus 0.7 times your age) as a starting point, or the Gulati formula if you’re a woman. Then pay attention to how the zones feel. If moderate-intensity exercise feels easy and you’re barely breathing hard, your true max is likely higher than your estimate. If you’re gasping at what should be a moderate pace, it may be lower.