Your target heart rate for exercise falls between 50% and 85% of your maximum heart rate, depending on how hard you want to work. To find it, you need two numbers: your estimated maximum heart rate and the intensity level you’re aiming for. The math is straightforward, and there are a few different formulas to choose from based on how precise you want to be.
Step 1: Estimate Your Maximum Heart Rate
Your maximum heart rate is the fastest your heart can beat during all-out effort. You don’t need to actually push yourself to that limit to find it. Two well-known formulas give you a reliable estimate using just your age.
The simplest and most widely used is the Fox formula: 220 minus your age. If you’re 40, your estimated max is 180 beats per minute (bpm). It’s been around since 1971 and remains the standard you’ll see in most gym charts and fitness apps.
A more accurate alternative is the Tanaka formula: 208 minus (0.7 × your age). For a 40-year-old, that gives 180 bpm. The two formulas happen to agree at age 40, but they diverge at other ages. At 60, for instance, Fox gives you 160 while Tanaka gives 166. Research from a large meta-analysis found a strong correlation between Tanaka’s equation and actual measured heart rates, and noted that the older Fox formula tends to underestimate max heart rate in older adults. That matters because underestimating your max means you might exercise at a lower intensity than you intend, or a stress test might understate your actual effort level. The Tanaka formula also performs better for overweight adults and younger active people.
Neither formula is perfect. Individual variation can swing your true max 10 to 12 bpm in either direction. But for planning a workout, these estimates are more than adequate.
Step 2: Pick Your Intensity Zone
The American Heart Association breaks exercise intensity into two main zones based on percentage of your maximum heart rate:
- Moderate intensity: 50% to 70% of max. This is brisk walking, easy cycling, or a casual swim. You can hold a conversation but you’re breathing noticeably harder than at rest.
- Vigorous intensity: 70% to 85% of max. This is running, fast cycling, or an intense group fitness class. Talking becomes difficult in short bursts.
Most general fitness goals, from heart health to weight management, are well served by moderate intensity. If you’re training for performance or trying to improve cardiovascular fitness more aggressively, vigorous intensity sessions are appropriate. Staying below roughly 85% of max keeps most people in a safe, sustainable range for regular training.
The Basic Calculation
Once you have your max heart rate and your target zone, the math is simple multiplication. Here’s an example for a 35-year-old aiming for moderate intensity using the Fox formula:
Max heart rate: 220 − 35 = 185 bpm
Lower end of moderate zone: 185 × 0.50 = 93 bpm
Upper end of moderate zone: 185 × 0.70 = 130 bpm
This person’s target range for moderate exercise is 93 to 130 bpm. For vigorous exercise, the same person would aim for 130 to 157 bpm (185 × 0.70 through 185 × 0.85).
A More Personalized Formula: Heart Rate Reserve
The percentage-of-max method treats everyone the same regardless of fitness level. A well-trained athlete with a resting heart rate of 50 bpm and a sedentary person resting at 80 bpm get identical targets if they’re the same age. The heart rate reserve method (sometimes called the Karvonen method) fixes this by factoring in your resting heart rate, which reflects your current cardiovascular fitness.
The formula works like this:
Heart rate reserve (HRR) = max heart rate − resting heart rate
Target heart rate = (HRR × desired intensity %) + resting heart rate
For that same 35-year-old with a resting heart rate of 65 bpm, aiming for 60% intensity:
HRR: 185 − 65 = 120 bpm
Target: (120 × 0.60) + 65 = 137 bpm
Compare that to the simple method at 60% of max, which gives 111 bpm. The heart rate reserve approach produces a higher, more realistic target because it accounts for where your heart starts. People in cardiac rehabilitation programs typically aim for 60% to 80% of heart rate reserve plus their resting heart rate. You can plug in whatever training zone percentage suits your goals.
How to Measure Your Resting Heart Rate
If you want to use the heart rate reserve method, you need an accurate resting heart rate. The most reliable readings come after you’ve been inactive for at least four minutes and haven’t recently exercised. Research on 24-hour heart rate patterns found that the truest resting values occur between 3:00 and 7:00 a.m., which is why many fitness trackers report a “sleeping” resting heart rate.
A practical approach: check your pulse first thing in the morning before getting out of bed, on a few different days, and average the results. Place two fingers on the inside of your wrist (thumb side) or along the side of your neck, count the beats for 15 seconds, and multiply by four. Doing this over several mornings smooths out any day-to-day variation from poor sleep or stress.
Checking Your Heart Rate During Exercise
A chest strap heart rate monitor or an optical sensor on a fitness watch gives you continuous, hands-free readings while you train. If you don’t have either, you can check manually. Pause briefly, find your pulse at your wrist or neck, count beats for 15 seconds, and multiply by four. It’s less precise, especially during vigorous exercise when your heart rate drops quickly once you stop, but it gives you a useful ballpark.
An alternative to heart rate monitoring altogether is the rating of perceived exertion (RPE) scale, which runs from 6 (no effort at all) to 20 (maximum effort). Research shows RPE correlates strongly with heart rate. An RPE of 11 to 13, which feels “light” to “somewhat hard,” corresponds roughly to moderate aerobic intensity and is a good target for less trained individuals. An RPE of 13 to 15 suits more intense but still aerobic training. If tracking numbers mid-workout feels disruptive, perceived exertion is a surprisingly reliable substitute.
When Standard Formulas Don’t Apply
Certain medications change the math entirely. Beta-blockers, commonly prescribed for high blood pressure and heart conditions, suppress both resting and peak heart rate. Someone on a beta-blocker who uses the standard 220-minus-age formula will get a target their heart physically cannot reach. Research on exercise programming for these patients found that all heart rate landmarks, including peak rate and the thresholds between aerobic and anaerobic effort, shift significantly lower. The heart rate reserve method performs better for people on beta-blockers than the simple percentage-of-max approach, but the recommended intensity is typically set lower (around 60% of reserve rather than 70%). If you take a beta-blocker or any medication that affects heart rate, the RPE scale or a supervised exercise test provides a more reliable way to gauge effort.
Age-based formulas also become less reliable at the extremes. They tend to overestimate max heart rate in younger adults and underestimate it in older adults, with the Fox formula showing more error than Tanaka’s. Women may see their max overestimated by about 5 bpm, while men using the Fox formula may see theirs underestimated by roughly 3 bpm. These gaps are small enough to be inconsequential for casual fitness, but worth knowing if your calculated zones don’t match how you actually feel during a workout. If 70% of your estimated max feels effortless, your true max is likely higher than the formula predicted.
Putting It All Together
For a quick target, use 220 minus your age, then multiply by 0.50 and 0.70 for moderate exercise or 0.70 and 0.85 for vigorous exercise. That gives you a range to aim for during your workout. If you want more precision, switch to the Tanaka formula (208 − 0.7 × age) for your max, measure your resting heart rate over several mornings, and apply the heart rate reserve calculation. The reserve method is especially worthwhile if you’re very fit or very sedentary, since it adjusts for your starting point rather than treating all people of the same age identically.
Whichever method you choose, treat the result as a guide, not a hard boundary. Your body gives you plenty of real-time feedback: breathing rate, the ability to talk, muscle fatigue. Heart rate targets work best as a complement to that internal feedback, not a replacement for it.