A healthy heart rate during exercise falls between 50% and 85% of your maximum heart rate, depending on how hard you’re pushing. For a 40-year-old, that translates to roughly 90 to 153 beats per minute. The exact range shifts with your age, your resting heart rate, and the type of workout you’re doing.
Target Heart Rate by Age
Your maximum heart rate is the ceiling your heart can sustain during all-out effort. The simplest way to estimate it: subtract your age from 220. A 30-year-old gets a max of 190 bpm, a 50-year-old gets 170 bpm. Your target zone for exercise sits between 50% and 85% of that number.
Here’s what that looks like across age groups, based on figures from the American Heart Association:
- 20 years: 100–170 bpm (max: 200)
- 30 years: 95–162 bpm (max: 190)
- 35 years: 93–157 bpm (max: 185)
- 40 years: 90–153 bpm (max: 180)
- 45 years: 88–149 bpm (max: 175)
- 50 years: 85–145 bpm (max: 170)
- 55 years: 83–140 bpm (max: 165)
- 60 years: 80–136 bpm (max: 160)
- 65 years: 78–132 bpm (max: 155)
- 70 years: 75–128 bpm (max: 150)
The lower end of those ranges (50–70% of max) corresponds to moderate exercise like brisk walking or an easy bike ride. The upper end (70–85% of max) is vigorous territory: running, fast cycling, or high-intensity interval training.
Why the 220-Minus-Age Formula Isn’t Perfect
The 220-minus-age formula has been used for decades, but it tends to underestimate max heart rate in older adults. A large meta-analysis found that a more accurate equation is 208 minus 0.7 times your age. For a 60-year-old, the classic formula gives a max of 160, while the updated formula gives 166. That six-beat difference matters when you’re calculating target zones, because it shifts the entire range upward. If you’re over 50 and your workouts feel too easy within the standard zones, the updated formula may give you a better target.
A More Personalized Calculation
The standard percentage-of-max approach ignores one important variable: your resting heart rate. Someone with a resting rate of 55 bpm has much more cardiac “room” than someone sitting at 80 bpm, even if they’re the same age. The Karvonen method accounts for this by working with your heart rate reserve, which is simply your max heart rate minus your resting heart rate.
To use it, take your heart rate reserve, multiply it by the percentage you want to train at, then add your resting heart rate back. For example, a 40-year-old with a resting heart rate of 65 bpm has a max of 180 and a reserve of 115. To find the lower end of a moderate zone (50%), you’d calculate 115 × 0.50 + 65 = 122 bpm. For the upper end of vigorous effort (85%), it’s 115 × 0.85 + 65 = 163 bpm. This produces a zone that reflects your actual fitness level, not just your age.
Fat Burning vs. Cardio Zones
Fitness trackers often label a “fat burn” zone and a separate “cardio” zone, which can make it seem like you need completely different workouts for each goal. The reality is more nuanced. Your body burns the highest proportion of fat at a moderate intensity, roughly 60% to 80% of your max heart rate. Peak fat burning occurs at about 54% of your maximum oxygen uptake, which for most people lands somewhere in that range.
But here’s the key finding: research shows those two zones overlap substantially. The fat-burning zone (roughly 68–87% of max heart rate in the study) and the aerobic fitness zone (59–76% of max) share a wide middle ground. In practical terms, a solid moderate-to-vigorous workout improves both fat metabolism and cardiovascular fitness at the same time. You don’t need to obsess over staying in one narrow band.
Signs Your Heart Rate Is Too High
Pushing above 85% of your max heart rate isn’t inherently dangerous for healthy people, but it’s difficult to sustain and not necessary for general fitness. If you’re gasping so hard you can’t speak a short sentence, feeling dizzy or lightheaded, experiencing chest tightness, or noticing an irregular or “fluttering” heartbeat, those are signals to slow down immediately. A useful rule of thumb: during moderate exercise, you should be able to talk but not sing. During vigorous exercise, you can get out a few words at a time but not hold a full conversation.
People who are new to exercise, returning after a long break, or managing a heart condition should start in the lower half of their target zone (50–60% of max) and build up gradually over weeks.
What Your Recovery Heart Rate Tells You
How fast your heart rate drops after you stop exercising is one of the simplest indicators of cardiovascular health. A healthy heart should slow down by more than 12 bpm within the first minute after peak effort. A drop of less than 12 bpm in that first minute is considered abnormal and is associated with higher long-term health risks. As your fitness improves over weeks and months of consistent training, you’ll typically see your recovery rate get faster, which is a reliable sign that your heart is getting stronger and more efficient.
To check this, note your heart rate at the moment you stop your hardest effort, then check again after 60 seconds of standing or slow walking. The difference between those two numbers is your one-minute heart rate recovery.
How to Track Your Heart Rate During Exercise
The easiest option is a wrist-based fitness tracker or smartwatch, which reads your pulse continuously using optical sensors. These are convenient but can lose accuracy during high-intensity or wrist-heavy movements like rowing or boxing. Chest strap monitors tend to be more accurate because they detect the electrical signal of each heartbeat directly.
If you don’t have a device, you can check manually. Place two fingers on the inside of your wrist or on the side of your neck, count the beats for 15 seconds, and multiply by four. Doing this right after a hard interval gives you a reasonable snapshot, though it’s less precise than continuous monitoring. Over time, learning to match how you feel (breathing rate, perceived effort) with your actual heart rate numbers helps you gauge intensity without stopping to check.