For most people, a good target heart rate during exercise falls between 50% and 85% of your maximum heart rate, depending on how hard you want to work. If you’re 40 years old, that translates to roughly 90 to 153 beats per minute. The exact number depends on your age, fitness level, and workout goals.
How to Find Your Maximum Heart Rate
Every target heart rate zone starts with one number: your estimated maximum heart rate. The simplest formula is 220 minus your age. A 30-year-old gets a max of 190 beats per minute (bpm). A 50-year-old gets 170. This formula, developed by Fox, Naughton, and Haskell in 1971, is still the most widely used in gyms and on fitness apps.
A more refined formula, published by Tanaka and colleagues in 2001, calculates it as 208 minus 0.7 times your age. For a 40-year-old, that gives 180 bpm instead of the 180 from the classic formula (they happen to match at 40). At younger and older ages, the two diverge slightly. The Tanaka formula tends to be more accurate for older adults, whose max heart rates the classic formula often underestimates. Either formula gives you a reasonable starting point, not a precise ceiling.
Target Zones for Different Goals
Heart rate zones divide the range between rest and your maximum into five tiers. Each one feels different and trains your body differently.
- Zone 1 (50% to 60% of max): Easy effort. You can hold a full conversation. This is your warm-up, cool-down, and recovery workout zone.
- Zone 2 (60% to 70% of max): Light effort. You can talk but might pause for a breath between sentences. This is where longer cardio sessions build endurance, and it’s the sweet spot for fat-burning walks and easy jogs.
- Zone 3 (70% to 80% of max): Moderate effort. Talking drops to short phrases. This zone builds both strength and cardiovascular endurance, and it’s where many steady-state runs and cycling sessions land.
- Zone 4 (80% to 90% of max): Hard effort. Speaking takes real work. You’re pushing toward your limit, building speed and power. Interval training often targets this zone.
- Zone 5 (90% to 100% of max): All-out effort. You’re gasping, not talking. Sprints and short bursts live here. This zone strengthens the heart at peak capacity and builds fast-twitch muscle fibers, but you can only sustain it for seconds to a couple of minutes.
For general health, the Mayo Clinic defines moderate-intensity exercise as 50% to 70% of your max and vigorous-intensity exercise as 70% to 85%. Most workout sessions should land somewhere in that combined range. If your goal is weight loss, higher intensity and longer duration both increase calorie burn, but consistency matters more than redlining every session.
Quick Reference by Age
Here’s what moderate (50% to 70%) and vigorous (70% to 85%) intensity look like at different ages, using the 220-minus-age formula:
- Age 25 (max 195): Moderate 98–137 bpm, vigorous 137–166 bpm
- Age 30 (max 190): Moderate 95–133 bpm, vigorous 133–162 bpm
- Age 35 (max 185): Moderate 93–130 bpm, vigorous 130–157 bpm
- Age 40 (max 180): Moderate 90–126 bpm, vigorous 126–153 bpm
- Age 45 (max 175): Moderate 88–123 bpm, vigorous 123–149 bpm
- Age 50 (max 170): Moderate 85–119 bpm, vigorous 119–145 bpm
- Age 55 (max 165): Moderate 83–116 bpm, vigorous 116–140 bpm
- Age 60 (max 160): Moderate 80–112 bpm, vigorous 112–136 bpm
- Age 65 (max 155): Moderate 78–109 bpm, vigorous 109–132 bpm
A More Personalized Calculation
The percentage-of-max approach ignores one important variable: how fit you already are. Two 45-year-olds with the same max heart rate can have wildly different resting heart rates. Someone who’s very fit might rest at 45 bpm, while a sedentary person might sit at 80 bpm. The fitter person has a much larger usable range.
The Karvonen method accounts for this by using your heart rate reserve, which is your maximum heart rate minus your resting heart rate. To find your target, multiply your heart rate reserve by the desired intensity percentage, then add your resting heart rate back in. For example, a 40-year-old with a resting heart rate of 60 bpm has a max of 180 and a reserve of 120. To work at 70% intensity: 120 × 0.70 = 84, plus the resting 60, gives a target of 144 bpm. This method produces slightly different (and generally more accurate) targets than straight percentage-of-max calculations.
To measure your resting heart rate, check your pulse first thing in the morning before getting out of bed, ideally over several days, and average the results. The more fit you become, the lower this number tends to drop. Very fit athletes often have resting rates in the 40 to 50 bpm range.
If You’re New to Exercise
Johns Hopkins Medicine recommends starting around 50% of your maximum heart rate if you haven’t been active. That might feel too easy at first, and that’s the point. Building a base at lower intensity reduces injury risk and lets your cardiovascular system adapt before you push harder. Over weeks, you can gradually move into higher zones as your body adjusts.
A practical test: if you can comfortably hold a conversation during your workout, you’re in the moderate range. If you can only get out a few words at a time, you’ve crossed into vigorous territory. This “talk test” is surprisingly well-correlated with heart rate zones and requires no gadgets at all.
When Heart Rate Monitors Get It Wrong
Wrist-based heart rate monitors (the kind built into smartwatches) are convenient but not always reliable. A systematic review covering 32 studies and over 1,000 participants found that accuracy varies widely by device, with some models showing mean percentage errors up to 20%. Accuracy also drops at higher exercise intensities and varies with skin tone. One study found that at higher intensities, wrist monitors showed errors of roughly 12 bpm for medium and darker skin tones compared to lighter skin tones at rest.
Chest strap monitors are significantly more accurate. The Polar H10, for example, shows a bias of only about 0.1 to 0.2 bpm compared to a medical-grade electrocardiogram. If you’re making training decisions based on heart rate data, a chest strap is worth the trade-off in comfort. If you’re using a wrist device, treat the readings as a rough guide rather than a precise measurement, especially during high-intensity intervals or activities with a lot of wrist movement.
Beta-Blockers and Other Medications
If you take beta-blockers for blood pressure or a heart condition, standard heart rate targets won’t apply to you. These medications deliberately slow the heart, and you may never reach your age-predicted target no matter how hard you push. There’s no simple formula to adjust for this, because the effect varies from person to person.
The best alternatives are a supervised exercise stress test, which can identify a realistic target heart rate while on medication, or using a perceived exertion scale instead. The Borg Rating of Perceived Exertion Scale lets you rate how hard you’re working based on your breathing, fatigue, and effort level rather than a number on your wrist. For most workouts, you should feel like you’re working “somewhat hard,” meaning it takes effort but you can keep going.
What Your Heart Rate After Exercise Tells You
How quickly your heart rate drops after you stop exercising is a useful marker of cardiovascular fitness. A healthy recovery is a drop of at least 18 beats per minute within the first minute of rest. The faster your heart rate comes down, the fitter your cardiovascular system. This is called heart rate recovery, and it improves as your fitness improves, giving you a built-in progress tracker beyond the scale or the mirror.
The initial drop in the first 30 to 60 seconds reflects your nervous system’s ability to shift out of “fight or flight” mode. A slower recovery phase continues over the next two to five minutes as your body returns to baseline. If your one-minute recovery consistently falls well below 12 beats, it may signal that your heart isn’t responding to rest the way it should.
Warning Signs to Stop
A high heart rate during intense exercise is expected. What isn’t normal is chest pain, dizziness, lightheadedness, fainting, sudden shortness of breath that’s out of proportion to your effort, or unusual weakness. These symptoms during a workout warrant stopping immediately, regardless of what your heart rate monitor reads. The number on your wrist matters less than how your body actually feels.