For most adults, a good cardio heart rate falls between 50% and 85% of your maximum heart rate, depending on how hard you want to push. Moderate-intensity cardio sits in the 50% to 70% range, while vigorous cardio lands between 70% and 85%. Your maximum heart rate is roughly 220 minus your age, which means a 40-year-old has a max of about 180 beats per minute (bpm) and a moderate cardio zone of roughly 90 to 126 bpm.
How to Find Your Maximum Heart Rate
The simplest formula is 220 minus your age. A 30-year-old gets a max of 190 bpm, a 50-year-old gets 170, and so on. A slightly refined version, sometimes called the Tanaka formula, calculates it as 208 minus 0.7 times your age. For a 40-year-old, that gives 180 instead of the same 180 from the simpler formula, but the two diverge more at younger and older ages.
Neither formula is perfect. Both tend to overestimate your true maximum heart rate, sometimes by around 6 bpm. The real number varies from person to person based on genetics, fitness level, and other factors that no age-based equation can capture. These formulas give you a useful starting point, not a precise ceiling. If you want your actual max, a supervised graded exercise test is the most reliable way to measure it.
Target Zones by Age
Here’s what the numbers look like using the 220-minus-age formula, with moderate intensity at 50% to 70% and vigorous intensity at 70% to 85%:
- Age 20 (max ~200 bpm): moderate 100–140, vigorous 140–170
- Age 30 (max ~190 bpm): moderate 95–133, vigorous 133–162
- Age 40 (max ~180 bpm): moderate 90–126, vigorous 126–153
- Age 50 (max ~170 bpm): moderate 85–119, vigorous 119–145
- Age 60 (max ~160 bpm): moderate 80–112, vigorous 112–136
- Age 70 (max ~150 bpm): moderate 75–105, vigorous 105–128
These ranges come from the American Heart Association’s guidelines. If your heart rate consistently falls below the moderate zone during a workout, you’re probably not getting much cardiovascular benefit. If it regularly pushes above 85% of max, you’re working at near-maximum effort, which is fine in short bursts but hard to sustain and unnecessary for general fitness.
Moderate vs. Vigorous Cardio
Moderate-intensity cardio, the 50% to 70% zone, is where your body primarily burns a mix of carbohydrates and fat using oxygen. Think brisk walking, easy cycling, or a relaxed swim. You can hold a conversation but you’re clearly working harder than at rest. This is the zone most associated with building a strong aerobic base, improving your heart’s efficiency, and burning calories over longer sessions.
Vigorous-intensity cardio, the 70% to 85% zone, pushes your body closer to its limit. Running, fast cycling, and high-intensity group classes typically land here. At this intensity, your muscles rely more heavily on stored carbohydrates because your body can’t deliver oxygen fast enough to keep up with demand. You can speak in short phrases but not carry on a full conversation. Vigorous cardio builds speed, power, and cardiovascular capacity more quickly per minute than moderate exercise.
Current federal guidelines recommend 150 minutes per week of moderate-intensity cardio, or 75 minutes of vigorous-intensity cardio, or some equivalent mix. Thirty minutes of brisk walking five days a week meets the moderate target. Three 25-minute runs per week meets the vigorous one. Going beyond these minimums provides additional health benefits.
A More Personalized Calculation
The percentage-of-max method is simple, but it ignores your resting heart rate, which varies a lot between individuals. A fit person with a resting rate of 55 bpm and a sedentary person with a resting rate of 80 bpm will have very different experiences at the same target number. The Karvonen method accounts for this by using something called heart rate reserve: the gap between your max and your resting heart rate.
Here’s how it works, step by step:
- Step 1: Calculate your max heart rate (220 minus your age).
- Step 2: Measure your resting heart rate first thing in the morning, before getting out of bed. Count your pulse for 60 seconds.
- Step 3: Subtract your resting heart rate from your max. That’s your heart rate reserve.
- Step 4: Multiply your heart rate reserve by the intensity percentage you want (for example, 0.60 for 60%), 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. At 60% intensity: 115 × 0.60 = 69, plus 65 = 134 bpm. Compare that to the simpler method, which gives 108 bpm at 60% of max. The Karvonen method produces a higher, more realistic target because it adjusts for your baseline fitness. If you’re already in decent shape and find that the basic percentage-of-max zones feel too easy, this method is worth trying.
Why Your Heart Rate Might Not Match the Charts
Several things can throw off your heart rate during exercise, making the standard zones misleading. Beta-blocker medications, commonly prescribed for high blood pressure and certain heart conditions, deliberately slow your heart rate. If you take one, you may never reach your calculated target heart rate no matter how hard you exercise. In that case, the standard charts don’t apply to you, and perceived effort becomes a better guide than any number on a wrist monitor.
Caffeine, dehydration, heat, and poor sleep can all push your heart rate higher than normal at the same effort level. If you usually jog at 140 bpm but hit 155 on a hot, humid day, you’re not suddenly fitter or working harder. Your heart is just pumping faster to cool your body. Similarly, stress and illness can elevate your resting and exercise heart rates by 10 to 20 bpm or more.
Fitness level matters too. As your cardiovascular system gets stronger over months of training, your heart pumps more blood per beat. That means a lower heart rate at the same pace. A workout that once put you at 160 bpm might eventually feel comfortable at 145. This is a sign of genuine improvement, not a reason to panic about being in the “wrong” zone.
Signs You’re Pushing Too Hard
Staying below 85% of your max for most workouts is a reasonable guideline, but the more important signals come from your body. Chest pressure, tightness, or pain during exercise is a red flag. So is unusual shortness of breath that feels disproportionate to how hard you’re working, or a racing, fluttering sensation in your chest. These warrant stopping immediately and getting evaluated.
For day-to-day training, a simpler check: if you can’t say a few words without gasping, you’re likely above 85% of max and deep into near-maximal effort. That’s fine for short intervals if you’re healthy and conditioned for it, but it shouldn’t be your default for every cardio session. Most of your weekly cardio minutes are best spent in the moderate zone, with occasional pushes into vigorous territory for variety and faster fitness gains.