The simplest way to estimate your max heart rate is to subtract your age from 220. A 40-year-old, for example, gets an estimated max of 180 beats per minute. But that formula can be off by 7 to 10 bpm in either direction, and for some people the error is even larger. If you want a more accurate number, you have better options: an updated formula, a DIY field test, or a clinical stress test.
The Age-Based Formulas
Two formulas are widely used. The classic one, developed by Fox in the 1970s, is the version most people know:
- Fox formula: 220 minus your age
- Tanaka formula: 208 minus (0.7 × your age)
The Tanaka formula, published in 2001, was built from a larger dataset and tends to be more accurate for older adults. For a 30-year-old, the two formulas give nearly identical results (190 vs. 187). But for a 60-year-old, they start to diverge: Fox predicts 160, while Tanaka predicts 166. That six-beat gap matters when you’re calculating training zones.
Neither formula is precise for any individual. A large analysis published in PLOS ONE found that all age-based equations produce typical errors of roughly 7 to 10 bpm, and the range of disagreement with lab-measured values spans about 18 to 24 bpm in either direction. That means your true max could easily be a full zone higher or lower than what the math suggests. These formulas are starting points, not gospel.
How to Test It Yourself
A field test gives you a real measurement instead of an estimate. The protocol recommended by the Norwegian University of Science and Technology’s exercise research group is straightforward and requires only a heart rate monitor (a chest strap is more reliable than a wrist sensor for max-effort work).
Start with a thorough warmup until you’re sweating. Then do two four-minute intervals at an intensity where you’re too breathless to hold a conversation, with three minutes of easy movement between them. Begin a third interval, and after two minutes, push your pace even harder and keep going until you physically can’t continue. The highest number your heart rate monitor records during that final push is your max heart rate.
If you don’t have a monitor, press two fingers against the side of your neck immediately after finishing. Count the beats for 30 seconds and double that number. It’s less precise than a monitor, but it gets you in the ballpark.
A few practical tips for a clean result: do the test when you’re rested and well-hydrated, not at the end of a training week. A hill or a treadmill set to a slight incline works well because the effort escalates naturally without requiring you to sprint at a pace that risks tripping or pulling a muscle. Running and cycling will often produce slightly different max heart rates because running recruits more total muscle mass. Test in the activity you actually train in.
The Clinical Option: A Stress Test
A graded exercise stress test in a clinic or hospital is the gold standard. You walk on a treadmill or pedal a stationary bike while electrodes on your chest feed a continuous EKG readout to a technician. The pace starts easy and increases in stages over roughly 10 to 15 minutes until you hit your limit. Because a medical team is watching your heart rhythm in real time, this is also the safest way to push to true max effort.
Stress tests are typically ordered for diagnostic reasons (checking for heart disease, evaluating chest pain) rather than for fitness curiosity. But if you’re on medications that affect heart rate, or if you have a known heart condition, a supervised test is the only reliable way to find your actual ceiling.
Why Your Number Might Be Lower Than Expected
Several things can suppress your max heart rate beyond what any formula accounts for. The most common is medication. Beta-blockers, prescribed for high blood pressure, irregular heart rhythms, and other cardiac conditions, work by slowing the heartbeat and reducing how hard the heart muscle contracts. If you’re taking one, standard formulas are essentially useless for you. The American Heart Association notes that beta-blockers affect everyone differently, so a brief supervised exercise test is the best way to establish your adjusted target heart rate.
Dehydration, sleep deprivation, and overtraining can also prevent you from reaching your true max during a field test. Heat and altitude push heart rate higher, which can create the illusion of a higher max when really your cardiovascular system is just under extra strain. For the most consistent reading, test in moderate conditions when you’re feeling fresh.
Who Should Skip the DIY Test
Max-effort testing is an inherently intense activity. People with valvular heart disease, hypertrophic cardiomyopathy, congenital heart conditions, or pulmonary hypertension face elevated risk during all-out exertion. Severe symptomatic aortic stenosis is considered an absolute reason not to do any form of exercise stress testing. If you have a diagnosed heart condition, get your max heart rate measured under medical supervision rather than on a trail or gym treadmill.
Even without a known condition, anyone over 45 who has been sedentary and wants to do a max-effort test should build a base of moderate exercise for several weeks first. The test demands a genuine all-out effort, and your body needs to be conditioned enough to safely produce one.
Putting Your Max Heart Rate to Use
Once you have a number you trust, you can set training zones as percentages of your max. A common framework breaks it down like this:
- 50 to 60%: Light activity, recovery walks
- 60 to 70%: Easy aerobic training, fat-burning zone
- 70 to 80%: Moderate aerobic training, the sweet spot for building endurance
- 80 to 90%: Threshold training, where conversation becomes impossible
- 90 to 100%: Max effort, sustainable for only short bursts
If your max is based on a formula, treat those zones as approximate. A 10-bpm error in your max cascades through every zone. If you find that your “easy” runs feel hard or your “hard” intervals feel too comfortable, your estimated max is probably off. That’s a good reason to do a field test and get a real number to work from.