Your target heart rate is a specific range of beats per minute that tells you you’re exercising hard enough to improve fitness but not so hard that you’re overdoing it. The American Heart Association defines two main targets: 50% to 70% of your maximum heart rate for moderate exercise, and 70% to 85% for vigorous exercise. Getting to those numbers takes a little math, starting with your estimated maximum heart rate.
Step 1: Estimate Your Maximum Heart Rate
The most common formula is simple: subtract your age from 220. A 40-year-old, for example, has an estimated max of 180 beats per minute (bpm). A 55-year-old lands at 165 bpm. This gives you the ceiling you’ll use to calculate your target zones.
A slightly more refined version, sometimes used in clinical settings, is 208 minus 0.7 times your age. For that same 40-year-old, this produces 180 bpm (essentially identical), but for a 55-year-old it gives 169.5 bpm rather than 165. The difference grows with age, and the revised formula tends to be more accurate for older adults. Neither formula is perfect. Both are population averages, meaning your true max could be 10 to 15 beats higher or lower. Current guidelines recommend treating any age-predicted max as an estimate, not an exact number.
Step 2: Calculate Your Target Range
Once you have your estimated max, multiply it by the percentage that matches your goal intensity. Here’s what that looks like for a 40-year-old with an estimated max of 180 bpm:
- Moderate intensity (50% to 70%): 90 to 126 bpm
- Vigorous intensity (70% to 85%): 126 to 153 bpm
That’s the basic method. If you want a more personalized number, the Karvonen method (also called heart rate reserve) factors in your resting heart rate, which reflects your current fitness level. The steps are: subtract your resting heart rate from your max, multiply by the desired percentage, then add your resting heart rate back in. For that 40-year-old with a resting rate of 65 bpm aiming for 70% intensity, it looks like this: (180 minus 65) times 0.70, plus 65, which equals about 146 bpm. Compare that to the simpler method, which gives 126 bpm at 70%. The Karvonen method produces a higher target because it accounts for the fact that a fitter heart (lower resting rate) has more “reserve” to work with.
How to Find Your Resting Heart Rate
A normal resting heart rate for most adults falls between 60 and 100 bpm. Athletes often sit in the 40s or 50s, while people who are less active tend toward the higher end of that range. Your resting rate is one of the simplest indicators of cardiovascular fitness, and you need it if you want to use the Karvonen method.
Measure it first thing in the morning before getting out of bed. Place the tips of your index and middle fingers on the inside of your wrist, in the groove between the bone and the tendon on the thumb side. Count the beats for a full 60 seconds. Some people count for 15 seconds and multiply by four, which is faster but slightly less accurate. Do this on three separate mornings and average the results.
Understanding Heart Rate Zones
Heart rate zones break intensity into five tiers based on percentages of your max. Each zone trains your body differently:
- Zone 1 (50% to 60%): Very light effort. Walking, warming up, active recovery between hard workouts.
- Zone 2 (60% to 70%): Light to moderate. This is the classic endurance-building zone, where you can hold a conversation comfortably. Long runs and easy cycling live here.
- Zone 3 (70% to 80%): Moderate to hard. Breathing gets noticeably heavier. Tempo runs and brisk uphill walking fall in this range.
- Zone 4 (80% to 90%): Hard. Sustained talking becomes difficult. Interval training and race-pace efforts push you here.
- Zone 5 (90% to 100%): Maximum effort. Sprints and all-out bursts that last only seconds to a couple of minutes.
For general fitness and fat loss, zones 1 through 3 are the sweet spot. Your body relies more heavily on stored fat for fuel during lower-intensity work. Zones 4 and 5 build speed and power but demand more recovery time and aren’t sustainable for long.
Checking Your Heart Rate During Exercise
The simplest approach is to stop briefly, find your pulse at your wrist or neck, and count for 15 seconds. Multiply that number by four. At the neck, press gently in the groove next to your windpipe with two fingers. Press too hard and you can briefly slow your heart rate, throwing off the count.
Wearable devices make continuous tracking easier. Chest straps that detect electrical signals from your heart are the most accurate consumer option. In direct comparisons, wrist-based optical sensors on smartwatches tend to track closely on average (within a couple of beats per minute for sustained steady effort), but they’re prone to occasional spikes of 30 to 40 bpm above the real number, particularly during activities with lots of wrist movement. If you’re using a wristwatch and a reading suddenly jumps well above what your effort level suggests, it’s likely a sensor glitch rather than a real spike. Chest straps rarely have this problem.
When the Numbers Don’t Apply
Certain medications change the equation entirely. Beta blockers, commonly prescribed for high blood pressure and some heart conditions, slow your heart rate and prevent it from climbing the way it normally would during exercise. If you take a beta blocker, your heart rate may never reach the target zones calculated from the standard formulas, even when you’re working hard. That doesn’t mean the exercise isn’t effective.
In these cases, a perceived exertion scale works better than a heart rate target. The Borg scale rates effort from 6 (no exertion at all) to 20 (absolute maximum). A rating of 12 to 14, which corresponds to “somewhat hard,” generally matches moderate-intensity exercise. You’re breathing faster, your muscles feel engaged, but you could keep going for a while. This scale also works well for anyone who finds the math annoying or doesn’t want to wear a device. Pay attention to your breathing, how your legs feel, and whether you could carry on a conversation. Those cues are surprisingly reliable.
Putting It All Together
For a quick starting point, subtract your age from 220 and aim for 50% to 70% of that number during moderate workouts, or 70% to 85% during harder sessions. If you want more precision, measure your resting heart rate over a few mornings and use the Karvonen formula to factor in your fitness level. Check your pulse periodically (or use a chest strap) to see where you land, and adjust your pace up or down to stay in the zone that matches your goal. If you’re on heart rate-lowering medication, skip the numbers and use perceived effort instead.
Keep in mind that these are starting points. As your fitness improves, your resting heart rate will likely drop, which shifts your target zones. Recalculating every few months keeps your training matched to your current fitness rather than where you were when you started.