The simplest 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). But this shortcut can be off by 10 to 12 bpm in either direction, which is a wide enough margin to throw off your training zones. More accurate options exist, from updated formulas to field tests to clinical stress tests.
The Common Formulas and Their Limits
The “220 minus age” formula dates back to 1971 and remains the most widely used estimate. It’s simple, but it was never based on rigorous original research, and its standard deviation of 10 to 12 bpm means a 35-year-old with a predicted max of 185 could actually peak anywhere from 173 to 197. That’s a huge range if you’re basing interval paces or heart rate zones on it.
A more refined formula, developed by researcher Hirofumi Tanaka, calculates max heart rate as 208 minus 0.7 times your age. For that same 35-year-old, Tanaka’s equation gives 183.5 bpm. The difference between the two formulas is small at younger ages and grows larger over time. By age 60, the old formula predicts 160 while Tanaka’s predicts 166. The Tanaka formula tends to be more accurate for older adults, who are exactly the group most likely to have their max heart rate underestimated by the classic equation.
Neither formula accounts for fitness level, sex, genetics, or medications. They give you a starting point, not a precise number.
How Max Heart Rate Changes With Age
Your maximum heart rate drops roughly 0.8 bpm per year as you age, but the rate of decline isn’t the same for everyone. Research published in Circulation found that highly fit individuals lose about 0.65 bpm per year, while those with low fitness levels lose closer to 1.07 bpm per year. Over a decade, that gap adds up: a fit person might lose 6 or 7 beats off their max, while a sedentary person loses 10 or 11.
This doesn’t mean exercise prevents the decline entirely. It means staying active slows it. And it’s another reason formulas based only on age can miss the mark, especially for people who are significantly more or less fit than average for their age group.
Field Tests You Can Do Yourself
If you want a number closer to your actual max, a field test is the most practical option. These require pushing yourself to full effort, so they’re best suited for people who already exercise regularly and have no known heart conditions.
A straightforward running-based approach works like this: warm up for 10 to 15 minutes at an easy pace, then run three minutes as hard as you can sustain. Your heart rate in the final 30 to 60 seconds of that effort will be at or very near your true maximum. A flat track or path works best since hills change the equation. Wearing a chest strap heart rate monitor gives you the most reliable reading during this kind of all-out effort.
You can also use a hill repeat test. After a thorough warmup, run hard up a steep hill for two to three minutes, jog back down, and repeat two more times. On the third repeat, push as hard as you possibly can. The peak reading on that final effort is typically your max or within a beat or two of it.
Both approaches demand genuine maximum effort, which is uncomfortable by design. If you finish feeling like you could have gone harder, the number you recorded isn’t your true max.
Clinical Stress Testing
The gold standard for measuring max heart rate is a graded exercise test in a clinical setting, usually on a treadmill. The most common protocol, called the Bruce Protocol, increases both speed and incline every three minutes until you can’t continue. You’re hooked up to an electrocardiogram the entire time, so the heart rate readings are precise and any rhythm abnormalities show up immediately.
In medical settings, the goal is usually reaching 85% of your age-predicted max (using the 220-minus-age formula) to adequately stress the heart for diagnostic purposes. But if you’re there specifically to find your true maximum, the test continues until you reach voluntary exhaustion.
Clinical testing makes the most sense if you have risk factors for heart disease, are over 45 and have been sedentary, or take medications that affect heart rate. For most healthy, active people, a well-executed field test gives a comparable result.
Factors That Alter Your Max
Several things can suppress your maximum heart rate or make a test unreliable.
- Beta-blockers: These medications lower peak heart rate by about 19 bpm on average. If you take one, any formula-based estimate or field test result will be meaningless unless adjusted. Your doctor can help you set appropriate training zones based on a modified scale.
- Altitude: At around 4,200 meters (roughly 13,800 feet), max heart rate drops by 16 to 18% compared to sea level. Even moderate elevations can shave a few beats off your peak. This effect is driven partly by increased activity in the part of the nervous system that slows the heart, and it persists even after days or weeks of acclimatization.
- Dehydration and heat: These raise your heart rate at any given effort level but can actually lower your achievable maximum because fatigue sets in sooner. A field test done on a hot day after inadequate hydration won’t reflect your true ceiling.
- Sport specificity: Max heart rate varies by activity. Most people reach their highest number while running because it uses more muscle mass than cycling or swimming. If you test on a bike, expect a result 5 to 10 bpm lower than what you’d see on a run.
How Accurate Are Wrist-Based Monitors?
Optical heart rate sensors on smartwatches have improved significantly, but they still struggle at peak effort. A study of Apple Watch accuracy found that at maximum performance levels, readings were off by an average of 6.3%, with individual measurements sometimes deviating by more than 20 bpm from the electrocardiogram reference. The watch tended to lose accuracy when heart rates were highest and movement was most intense, which is exactly the moment that matters during a max heart rate test.
Chest strap monitors that use electrical signals (similar to a simplified EKG) are far more reliable during high-intensity efforts. If you’re doing a field test specifically to find your max, a chest strap is worth using. For everyday training where you just need to stay in a general zone, a wrist sensor is usually good enough.
Putting Your Number to Use
Once you have a max heart rate, whether estimated or tested, you can set meaningful training zones. A common five-zone model breaks effort into recovery (50 to 60% of max), easy aerobic (60 to 70%), moderate aerobic (70 to 80%), threshold (80 to 90%), and max effort (90 to 100%). These percentages become far more useful when the underlying max number is accurate.
If you used a formula, treat it as an approximation and adjust based on real-world experience. If your “easy” zone feels hard, or your “threshold” zone feels comfortable enough to hold a conversation, your estimated max is probably off. Retesting every few years also makes sense, since that 0.8 bpm annual decline quietly shifts all your zones downward over time.