The most common way to calculate 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. It’s simple, widely used, and good enough for most people setting up training zones or gauging workout intensity. But it comes with a margin of error that’s worth understanding, and a few alternative formulas can get you closer to your true number.
The Standard Formula: 220 Minus Age
This formula, often called the Fox formula, has been the default in gyms, on cardio machines, and in clinical settings for decades. You just subtract your age from 220 to get your estimated maximum heart rate (MHR) in beats per minute:
- MHR = 220 − your age
It works as a quick reference, but it’s far from precise. The standard deviation falls between 10 and 12 beats per minute, meaning your actual max could easily be 10 or more beats higher or lower than the formula predicts. In formal testing, the formula’s limits of agreement stretch roughly 23 beats in either direction. That’s a wide range. The formula also tends to overestimate max heart rate in younger adults and underestimate it in older adults, which is a consistent finding across studies.
Alternative Formulas Worth Knowing
Researchers have developed other equations that attempt to correct for the age-related bias in the 220-minus-age approach. The two most cited alternatives are:
- Tanaka formula: MHR = 208 − (0.7 × age)
- Gulati formula: MHR = 206 − (0.88 × age), developed specifically from data on women
The Tanaka formula tends to give slightly higher estimates for people over 40 and slightly lower estimates for younger adults compared to the Fox formula. For a 50-year-old, the Fox formula yields 170 bpm, while Tanaka gives 173 bpm. The gap widens with age. For a 70-year-old, Fox predicts 150 bpm and Tanaka predicts 159 bpm, which better reflects what older adults actually achieve on treadmill tests.
The Gulati formula was derived from a large study of asymptomatic women and addresses evidence that sex influences how max heart rate changes with age. A 45-year-old woman would get 175 bpm from the Fox formula but about 166 bpm from the Gulati formula.
None of these formulas eliminate the margin of error entirely. They all carry a standard deviation of roughly 10 bpm. But if you’re over 50 or female, the Tanaka or Gulati formulas may give you a more realistic starting point.
Using Heart Rate Reserve for Training Zones
Once you have your estimated max heart rate, you can use it to set training zones. The simplest approach is to take a percentage of your max. Moderate exercise typically falls between 50% and 70% of MHR, and vigorous exercise between 70% and 85%.
A more personalized method factors in your resting heart rate using a calculation called the Karvonen formula, or heart rate reserve (HRR) method:
- Heart rate reserve = max heart rate − resting heart rate
- Target heart rate = (HRR × desired intensity %) + resting heart rate
This matters because two people with the same max heart rate can have very different resting heart rates. Someone who is very fit might rest at 52 bpm, while someone less active might rest at 75 bpm. The fitter person has a larger reserve to work with, and the Karvonen method captures that difference. To use it, measure your resting heart rate first thing in the morning before getting out of bed, ideally averaged over a few days.
For example, a 35-year-old with a resting heart rate of 60 bpm would have a max of 185 (using the Fox formula) and a heart rate reserve of 125. To exercise at 70% intensity, their target would be (125 × 0.70) + 60 = 148 bpm. Using the simpler percentage-of-max method, 70% of 185 is just 130 bpm. The difference is significant enough to change how hard you’re actually working.
Why Max Heart Rate Drops With Age
Your maximum heart rate declines roughly one beat per minute for every year you age, regardless of fitness level. Even elite athletes experience this. The cause is primarily structural changes in the heart’s natural pacemaker, a cluster of cells called the sinoatrial node.
As you get older, collagen (fibrous tissue) builds up in the heart’s upper chambers, and the pacemaker cells lose some of their ability to fire rapidly. Specifically, certain proteins that control electrical signaling in the heart decrease with age, slowing the rate at which the pacemaker can generate and spread electrical impulses. This reduction in the heart’s intrinsic rhythm is the single biggest contributor to age-related decline in max heart rate.
On top of that, the heart becomes less responsive to adrenaline-like signals that normally speed it up during exercise. The receptors on heart cells that receive these signals decrease in number and become less efficient. Together, these two mechanisms (a slower intrinsic rhythm and a blunted response to stress hormones) account for most of the decline. Fitness training doesn’t reverse these changes, though it does improve how efficiently your heart pumps blood at any given heart rate.
How Beta-Blockers Change the Picture
If you take beta-blockers for blood pressure, heart rhythm issues, or anxiety, standard formulas won’t apply to you in the usual way. Beta-blockers work by blocking the same adrenaline receptors that drive your heart rate up during exercise, so they consistently lower the max heart rate you can actually reach.
Research from a large exercise testing study found that people on beta-blockers achieved about 8% lower max heart rates compared to people not taking them, regardless of sex or heart disease status. For someone with a predicted max of 180, that’s roughly 14 to 15 fewer beats per minute, which substantially changes where your training zones fall.
If you’re on beta-blockers and using heart rate to guide exercise, the standard percentage targets don’t translate directly. A threshold of about 65% of your predicted max on beta-blockers corresponds to roughly the same fitness signal as hitting 85% of predicted max without medication. Working with a rate of perceived exertion scale (how hard the exercise feels on a 1 to 10 scale) is often more practical than chasing a specific number on your watch.
How Accurate Do You Really Need to Be?
For most people using heart rate zones to guide cardio workouts, the 220-minus-age formula is a reasonable starting point. The margin of error matters most when your training is highly structured or when medical decisions depend on hitting specific heart rate targets during a stress test.
If you find that the predicted zones feel too easy or impossibly hard, your actual max likely differs from the estimate. The only way to know your true maximum heart rate is through a graded exercise test, typically done on a treadmill or bike in a clinical or sports performance lab, where intensity increases until you physically can’t sustain it. Some fitness-focused facilities offer this outside of a medical setting as well.
Short of formal testing, you can get a rough real-world estimate by doing an all-out effort at the end of a hard interval session (after a thorough warmup) and checking the peak reading on a chest strap heart rate monitor. Wrist-based monitors are less reliable at very high heart rates. Whatever number you get, treat it as a better anchor than any formula, and build your training zones from there.