Your heart rate during exercise should generally fall between 50% and 85% of your maximum heart rate, depending on how intense you want your workout to be. To find your estimated maximum, subtract your age from 220. A 40-year-old, for example, has an estimated max of 180 beats per minute (bpm), so their target range during exercise would be roughly 90 to 153 bpm.
That single formula gives you a starting point, but the real answer depends on your fitness goals, your sex, your resting heart rate, and whether you take certain medications. Here’s how to dial it in.
How to Estimate Your Maximum Heart Rate
The most common formula is simply 220 minus your age. It’s quick and widely cited by the American Heart Association, but it can be off by 10 to 12 beats per minute in either direction. A more refined version, sometimes called the Tanaka formula, multiplies your age by 0.7 and subtracts the result from 207. For a 50-year-old, the standard formula gives a max of 170 bpm, while the Tanaka version gives 172. The gap widens at younger and older ages.
For women specifically, the standard formula tends to overestimate max heart rate in younger women and underestimate it in older women. Research from the St. James Women Take Heart Project produced a sex-specific formula: 206 minus 0.88 times your age. For a 40-year-old woman, that yields about 171 bpm instead of the 180 the standard formula predicts. This difference matters. Overestimating your max can push target zones too high, making workouts feel impossibly hard or leading you to think you’re underperforming when you’re actually right on track.
The Five Heart Rate Zones
Once you know your estimated max, you can break your effort into five zones. Each one feels different and trains your body in a different way.
Zone 1 (50% to 60% of max): You can hold a full conversation without pausing. This is warm-up, cool-down, and recovery territory. Think of an easy walk or gentle cycling after a hard training day.
Zone 2 (60% to 70% of max): Light conversation is still possible, but you might need to pause for a breath now and then. This is the sweet spot for longer cardio sessions that build endurance without beating you up. Most of a beginner’s training and a surprising amount of experienced runners’ mileage falls here.
Zone 3 (70% to 80% of max): Talking drops off because your breathing picks up noticeably. The effort feels comfortably hard. This zone builds both strength and aerobic endurance, and it’s where a brisk jog or moderate cycling class typically lands.
Zone 4 (80% to 90% of max): Speaking takes real effort. You’re pushing toward your limit, building speed and power. Interval training and tempo runs live in this zone.
Zone 5 (90% to 100% of max): You’re gasping, not talking. This is an all-out sprint that you can only sustain for short bursts. It trains your heart at peak capacity and recruits fast-twitch muscle fibers. Most people only visit Zone 5 during structured interval work.
What Counts as Moderate vs. Vigorous Exercise
Federal physical activity guidelines recommend at least 150 minutes per week of moderate-intensity exercise or 75 minutes of vigorous-intensity exercise. In heart rate terms, moderate intensity falls roughly in Zone 2 and the lower end of Zone 3 (about 64% to 76% of your max). Vigorous intensity covers the upper end of Zone 3 through Zone 4 (roughly 77% to 93% of your max). If your goal is simply to meet the guidelines for general health, staying in that moderate range during a brisk walk, swim, or bike ride gets you there.
A More Personalized Calculation
The percentages above use your max heart rate alone, but your resting heart rate matters too. Two people the same age can have very different resting rates. Someone with a resting heart rate of 55 bpm has more “room” between rest and max than someone resting at 75 bpm. The Karvonen method accounts for this by using what’s called heart rate reserve: your max minus your resting heart rate.
Here’s how it works. Say you’re 35 with a resting heart rate of 65 bpm. Your estimated max is 185. Your heart rate reserve is 185 minus 65, which equals 120. To find a target for Zone 2 (60% to 70%), multiply 120 by 0.60 and 0.70, then add your resting heart rate back in. That gives you a range of 137 to 149 bpm. Compare that to the simpler method, which would put Zone 2 at 111 to 130 bpm. The Karvonen approach produces a higher, often more realistic target for people who are already reasonably fit.
To use this method, measure your resting heart rate first thing in the morning before getting out of bed. Take it on three or four consecutive days and average the results for accuracy.
Why Your Heart Rate Might Not Match the Charts
Several factors can shift your heart rate response to exercise. Heat, dehydration, caffeine, poor sleep, and stress all push heart rate higher at a given effort level. Altitude does the same, especially in the first few days before your body adjusts.
Medications are one of the biggest variables. Beta blockers, commonly prescribed for high blood pressure and certain heart conditions, slow the heart rate and can prevent it from climbing to your normal target zone during exercise. If you take a beta blocker and try to hit a target based on 220 minus your age, you may never get there, no matter how hard you push. In that case, perceived exertion is a better guide. The Borg Rating of Perceived Exertion Scale asks you to rate your effort on a scale from 6 (no effort at all) to 20 (maximum effort). A moderate workout falls around 12 to 14 on that scale. You can also use the talk test: if you can speak in short sentences but not sing, you’re in the moderate zone.
Fitness level also plays a role over time. As your cardiovascular fitness improves, your heart pumps more blood per beat, so your heart rate at the same pace or resistance will gradually drop. A workout that once pushed you into Zone 4 may eventually feel like Zone 3. That’s a sign of progress, not a sign you need to panic about lower numbers.
How to Use Heart Rate Zones in Practice
If you’re new to exercise or returning after a break, spending most of your time in Zones 1 and 2 builds a strong aerobic base without overtaxing your body. A common beginner mistake is pushing into Zone 4 every session, which leads to fatigue and burnout.
For general fitness, a practical weekly mix looks like 80% of your training time in Zones 1 and 2, with the remaining 20% in Zones 3 through 5. This is sometimes called the 80/20 rule, and it’s used by recreational exercisers and elite endurance athletes alike. The easy sessions build your aerobic engine, while the harder sessions sharpen speed and power.
A chest strap heart rate monitor gives the most accurate real-time readings. Wrist-based optical sensors on smartwatches have improved significantly but can lag during quick changes in intensity and sometimes misread during activities with a lot of wrist movement. For steady-state cardio like jogging or cycling, wrist monitors are generally reliable enough to guide your training.