A good heart rate for exercise falls between 50% and 85% of your maximum heart rate, depending on how hard you want to work. For moderate exercise like brisk walking, aim for 50% to 70% of your max. For vigorous exercise like running or cycling hard, aim for 70% to 85%. Your maximum heart rate is roughly 220 minus your age, so a 40-year-old has an estimated max of 180 beats per minute.
How to Find Your Target Range
The simplest method starts with that 220-minus-age formula. A 30-year-old has an estimated max of 190 bpm, putting their moderate-intensity zone at roughly 95 to 133 bpm and their vigorous zone at 133 to 162 bpm. A 50-year-old, with a max around 170, would aim for 85 to 119 bpm during moderate exercise and 119 to 145 bpm during vigorous work.
This formula gives you a ballpark. A more personalized approach factors in your resting heart rate, which reflects your current fitness level. The calculation, sometimes called the Karvonen method, works like this: subtract your resting heart rate from your maximum heart rate to get your “heart rate reserve,” then multiply that number by the percentage you want to train at, and add your resting heart rate back. Someone with a resting heart rate of 60 and a max of 190 has a reserve of 130. Training at 60% intensity would mean (130 × 0.60) + 60 = 138 bpm. This method tends to give more accurate targets, especially if your resting heart rate is unusually high or low.
The Five Heart Rate Zones
Heart rate zones break your effort into five tiers, each measured as a percentage of your maximum heart rate. They help you train with purpose rather than just guessing how hard to push.
- Zone 1 (50% to 60%): Very light effort. Walking, gentle warm-ups, active recovery days. You can hold a full conversation easily.
- Zone 2 (60% to 70%): Light to moderate effort. Brisk walking, easy jogging. Your body draws a greater proportion of energy from fat in this zone, making it popular for longer, steady workouts that build aerobic endurance.
- Zone 3 (70% to 80%): Moderate to hard effort. Running at a comfortable pace, steady cycling. Your body shifts toward burning carbohydrates because they generate energy faster. You can talk in short sentences but not comfortably carry on a long conversation.
- Zone 4 (80% to 90%): Hard effort. Tempo runs, fast intervals. Carbohydrates become the dominant fuel source. Talking is difficult. This zone improves your lactate threshold, meaning your body gets better at clearing the byproducts of intense effort.
- Zone 5 (90% to 100%): All-out effort. Sprints, race finishes. Sustainable for only short bursts, typically under a few minutes. This zone builds raw speed and power but isn’t necessary for general fitness.
Most people benefit from spending the majority of their exercise time in zones 2 and 3, with occasional sessions pushing into zones 4 and 5.
What Affects Your Heart Rate During Exercise
The same workout can produce noticeably different heart rate numbers depending on conditions. Heat and humidity force your heart to work harder because blood gets diverted to the skin for cooling. You might see your heart rate run 10 to 20 beats higher on a hot day compared to a cool one, even at the same pace.
Altitude has a similar effect. With less oxygen available, your heart compensates by pumping faster to deliver more blood to working muscles. Cold, wind chill, and even jet lag can amplify the stress. Caffeine raises heart rate modestly in some people, as does dehydration. If your numbers look unusually high on a given day, consider whether any of these factors are at play before assuming you’re out of shape.
When Heart Rate Monitors Get It Wrong
Wrist-based heart rate sensors, the kind built into most smartwatches, use light to detect blood flow through the skin. They work reasonably well during steady-state exercise but can lose accuracy during high-intensity or variable movements. One study comparing wrist monitors to chest straps found that wrist readings on a stationary bike averaged around 105 to 106 bpm while the chest strap recorded 127 bpm for the same effort. That’s a gap large enough to put you in the wrong training zone entirely.
Chest strap monitors use electrical signals similar to an EKG and are generally more reliable during intense or erratic movement. If you’re serious about training by heart rate, a chest strap gives you more trustworthy data. If you’re using a wrist device casually, treat the numbers as estimates rather than exact targets.
Why Medications Change the Rules
Beta-blockers, commonly prescribed for high blood pressure and certain heart conditions, slow your heart rate by design. If you take one, your heart rate during exercise won’t rise the way it normally would, and standard target heart rate formulas become unreliable. You could be working hard but see a number that suggests you’re barely trying.
In this situation, the “talk test” and perceived exertion scales are more useful than a heart rate monitor. Most workouts should feel somewhat hard: you’re putting in real effort, breathing noticeably heavier, but you can still get a few words out. If you can’t talk at all, you’re likely pushing too hard. If you can sing, you’re not pushing enough.
Signs You’re Pushing Too Hard
Your heart rate climbing above your target zone for a few seconds isn’t dangerous on its own. But certain symptoms during exercise are red flags regardless of what your monitor says: chest pain or pressure, dizziness or lightheadedness, feeling faint, sudden weakness, or shortness of breath that feels disproportionate to your effort. If you experience any of these, stop exercising.
A racing or pounding heartbeat that feels irregular, with a flopping or skipping sensation, is also worth paying attention to. A fast heart rate during exercise is completely normal. A heart rate that feels chaotic or doesn’t come down after you stop is a different matter.
How Quickly Your Heart Rate Recovers Matters
One of the most useful numbers isn’t your heart rate during exercise but how fast it drops afterward. Heart rate recovery, measured one minute after you stop intense exercise, is a strong indicator of cardiovascular fitness. A drop of 18 beats or more in that first minute is considered good. A smaller drop can suggest your cardiovascular system is under more strain than it should be, or that your fitness level has room for improvement.
Tracking this number over weeks and months gives you a clearer picture of fitness progress than your exercise heart rate alone. As your cardiovascular system gets stronger, your heart rate will recover faster after hard efforts, even if your peak numbers during exercise stay roughly the same.