Your target heart rate zone is a range of beats per minute (bpm) that tells you how hard to push during exercise. To find it, you need two numbers: your maximum heart rate and the percentage of that max you want to train at. The simplest approach takes about 10 seconds of math.
The Simple Formula: 220 Minus Your Age
The most widely used method estimates your maximum heart rate by subtracting your age from 220. A 40-year-old, for example, has an estimated max of 180 bpm. From there, you multiply that number by the percentage range for your desired intensity level.
For moderate-intensity exercise, the American Heart Association recommends working at 50% to 70% of your max. For vigorous exercise, the range is 70% to 85%. So that same 40-year-old aiming for moderate intensity would calculate:
- Lower end: 180 × 0.50 = 90 bpm
- Upper end: 180 × 0.70 = 126 bpm
For a vigorous workout, the range would be 126 to 153 bpm. This formula is a rough estimate, not a precise measurement. Individual max heart rates can vary by 10 to 20 beats from the prediction. But for most people starting a fitness routine, it’s a perfectly useful starting point.
The Karvonen Formula: A More Personalized Approach
The Karvonen method factors in your resting heart rate, which makes it more tailored to your actual fitness level. Someone with a resting heart rate of 55 bpm is in a different cardiovascular starting position than someone at 80 bpm, and this formula accounts for that gap.
Here’s how it works, step by step:
- Step 1: Estimate your max heart rate (220 minus your age).
- Step 2: Subtract your resting heart rate from your max. This gives you your heart rate reserve.
- Step 3: Multiply your heart rate reserve by your target percentage.
- Step 4: Add your resting heart rate back to that number.
For a 40-year-old with a resting heart rate of 65 bpm, targeting 70% intensity:
Max heart rate: 180. Heart rate reserve: 180 − 65 = 115. Then 115 × 0.70 = 80.5. Finally, 80.5 + 65 = 145.5 bpm. Compare that to the simpler formula, which would give 126 bpm at 70%. The Karvonen method produces a higher target because it’s calibrated to your individual baseline, not just your age.
How to Measure Your Resting Heart Rate
If you want to use the Karvonen formula, you need an accurate resting heart rate. The best time to measure it is first thing in the morning, before you get out of bed. Place two fingers (index and middle) on the inside of your wrist, just below the base of your thumb, and count the beats for 30 seconds. Multiply by two.
Avoid measuring within one to two hours after exercise or a stressful event. Caffeine can also elevate your pulse, so wait at least an hour after your morning coffee. Sitting or standing for a long stretch beforehand can skew the reading as well. Take the measurement on a few different mornings and average the results for the most reliable number. For most adults, resting heart rate falls between 60 and 100 bpm, with fitter individuals often landing in the 50s or lower.
Quick Reference Chart by Age
This chart uses the simple 220-minus-age formula with a target zone of 60% to 85% of max heart rate, covering moderate through vigorous exercise.
- Age 20: Max 200 bpm, target zone 120–170 bpm
- Age 30: Max 190 bpm, target zone 114–162 bpm
- Age 40: Max 180 bpm, target zone 108–153 bpm
- Age 50: Max 170 bpm, target zone 102–145 bpm
- Age 60: Max 160 bpm, target zone 96–136 bpm
- Age 70: Max 150 bpm, target zone 90–123 bpm
If your age falls between these benchmarks, you can run the math yourself or simply split the difference. A 35-year-old would have a max of roughly 185 bpm and a target zone of about 111 to 157 bpm.
The Five Training Zones Explained
If you use a fitness watch or train for endurance events, you’ve probably seen heart rate broken into five zones rather than just “moderate” and “vigorous.” Each zone corresponds to a percentage of your max heart rate and produces different physiological effects.
Zone 1 (50%–60% of max) is your warm-up and recovery zone. Effort is light, conversation is easy, and your body burns primarily fat for fuel. This is the pace of a casual walk or cool-down jog.
Zone 2 (60%–70%) is the endurance-building zone where most long, steady cardio should happen. Your body still relies mainly on fat for energy, and you can sustain this pace for extended periods. It’s ideal for building an aerobic base while limiting injury risk.
Zone 3 (70%–80%) is a moderate-to-hard effort, sometimes called the tempo zone. Your body starts drawing on a mix of fat, carbohydrates, and protein. Breathing gets noticeably harder but stays manageable. This zone builds both strength and endurance.
Zone 4 (80%–90%) is a hard effort near your lactate threshold, the point where your muscles produce waste faster than your body can clear it. You’re burning mostly carbohydrates here, and you can only sustain this intensity for shorter intervals. It’s where speed and power improve.
Zone 5 (90%–100%) is an all-out, peak effort. You’re working at or near your maximum heart rate, building fast-twitch muscle fibers and forcing your cardiovascular system to its ceiling. Think sprints or the final push of a race. Most people can hold this for only a minute or two.
When Heart Rate Formulas Don’t Apply
Beta blockers and certain other blood pressure medications deliberately slow your heart rate, which means the standard formulas will overestimate your target zone. If you take a medication that keeps your heart rate from rising the way it normally would during exercise, heart rate alone isn’t a reliable intensity gauge.
An alternative is the Borg Rating of Perceived Exertion scale, which asks you to rate how hard you feel you’re working based on your breathing, fatigue, and overall effort. On a scale from 6 to 20, moderate exercise typically falls around 12 to 14 (you’re breathing harder but can still talk), while vigorous effort lands around 15 to 17. This approach works regardless of what medications you take because it tracks how your body actually feels, not just your pulse.
Perceived exertion is also useful if you suspect the 220-minus-age formula doesn’t fit you well. Some people have naturally high or low max heart rates that deviate significantly from the prediction. If you’re hitting your calculated target zone but the effort feels absurdly easy or impossibly hard, your true max likely differs from the estimate. Pairing heart rate data with a perceived exertion check gives you a more complete picture of how hard you’re actually working.