Heart rate zones are five intensity levels based on percentages of your maximum heart rate, and they tell you exactly how hard your body is working during exercise. Each zone triggers different responses in your body, from burning fat at lower intensities to building speed and power near your peak. Once you know your max heart rate and the percentage ranges for each zone, you can calculate your personal numbers in under a minute.
How to Find Your Max Heart Rate
Everything starts with your maximum heart rate (MHR), the fastest your heart can beat during all-out effort. The simplest estimate is the classic formula: 220 minus your age. If you’re 35, that gives you a max of 185 beats per minute (bpm). It’s easy to remember, but it comes with a significant margin of error: the standard deviation is plus or minus 15 bpm. That means your true max could be anywhere from 170 to 200 in this example.
A more refined formula, developed by researcher Hirofumi Tanaka, calculates MHR as 208 minus 0.7 times your age. For a 35-year-old, that’s 183.5 bpm. There are also sex-specific formulas: for men, 208 minus 0.8 times age; for women, 201 minus 0.63 times age. These tend to be more accurate across different fitness levels, but no age-based formula is perfect. If you want a precise number, a graded exercise test supervised by a professional is the gold standard.
The Five Heart Rate Zones
Zone 1: 50% to 60% of Max
This is warmup and cooldown territory. Your body burns mostly fat for fuel, and the effort feels easy enough that you could hold a full conversation without pausing to breathe. It’s also the right zone for recovery workouts, the kind of light movement you do the day after a hard session. For someone with a max heart rate of 185, Zone 1 falls between roughly 93 and 111 bpm.
Zone 2: 60% to 70% of Max
Zone 2 is where endurance is built. Your body still relies primarily on fat as fuel, and the pace feels comfortable but purposeful. You can talk, though you might need an occasional breath between sentences. Long runs, steady bike rides, and brisk walks typically land here. About 65% of the calories you burn in this zone come from fat, which is why it’s sometimes called the “fat-burning zone.” Using our 185 bpm example, Zone 2 runs from about 111 to 130 bpm.
Zone 3: 70% to 80% of Max
The effort picks up noticeably. Your body starts pulling from a mix of fat, carbohydrates, and protein for energy. Conversation becomes choppy. This zone builds both strength and aerobic endurance, and it’s where many people naturally settle during a moderately hard workout. For a max of 185, that’s roughly 130 to 148 bpm.
Zone 4: 80% to 90% of Max
Zone 4 is hard. You’re approaching your redline, and your body shifts to burning mostly carbohydrates and protein because it needs fuel it can access quickly. Talking is limited to a few words at a time. Tempo runs, hill repeats, and race-pace intervals live in this zone. It improves your speed, your lactate tolerance, and your ability to sustain high effort. With a 185 max, Zone 4 spans about 148 to 167 bpm.
Zone 5: 90% to 100% of Max
This is maximum effort, the kind you can sustain for only short bursts, typically 30 seconds to a few minutes. Your heart works at peak capacity, and the primary benefit is building fast-twitch muscle fibers and raw power. Sprints, all-out cycling intervals, and competitive race finishes push you here. For a 185 max, Zone 5 is roughly 167 to 185 bpm.
Why the “Fat-Burning Zone” Is Misleading
Fitness trackers and gym equipment love to highlight the fat-burning zone, which corresponds to Zone 2. And it’s true: a higher percentage of calories burned at that intensity comes from fat (around 65%). But that number is a percentage of a smaller total. When you move into Zone 3 (the aerobic zone at 70% to 80% of max), only about 45% of calories come from fat, yet you’re burning significantly more total calories per minute. The result is that higher-intensity exercise often burns more total fat in the same amount of time, even though the fat percentage is lower.
Zone 2 still has enormous value for endurance, recovery, and building your aerobic base. But if your primary goal is losing body fat, total calorie expenditure matters more than the fuel-source ratio on any single workout.
A More Personalized Calculation
The basic percentage method treats everyone with the same max heart rate identically, regardless of fitness level. A more personalized approach uses your heart rate reserve (HRR), which factors in your resting heart rate. The formula is simple: subtract your resting heart rate from your max heart rate. That gap is your reserve.
To find a zone target, multiply your HRR by the desired percentage, then add your resting heart rate back. For example, if your max is 185 and your resting heart rate is 60, your HRR is 125. To find the bottom of Zone 2 (60%), you’d calculate 125 × 0.60 + 60 = 135 bpm. This method, sometimes called the Karvonen method, produces more accurate targets because a well-trained person with a resting heart rate of 50 will get different zones than a beginner with a resting rate of 75, even if they’re the same age.
To use this method, measure your resting heart rate first thing in the morning before getting out of bed, ideally averaged over several days. Most fitness watches track this automatically.
Training Without a Heart Rate Monitor
If you don’t have a chest strap or wrist sensor, you can estimate your zone using perceived exertion. The Borg RPE scale rates effort from 6 (no exertion at all) to 20 (absolute maximum). A rating of 12 to 14 corresponds to moderate or “somewhat hard” effort, which roughly aligns with Zones 2 and 3. A rating of 15 to 17 (“hard” to “very hard”) maps to Zones 4 and low 5.
The simplest shortcut is the talk test. If you can speak in full sentences, you’re in Zones 1 or 2. If you can manage only short phrases, you’re in Zone 3 or 4. If you can barely get out a word, you’re in Zone 5. It’s not precise, but it’s surprisingly reliable for keeping your easy days easy and your hard days hard.
How to Spend Your Time Across Zones
Most endurance athletes and coaches follow an approach often called polarized training: roughly 80% of weekly training time in Zones 1 and 2, and the remaining 20% in Zones 4 and 5. Zone 3 gets the least intentional time because it’s hard enough to create fatigue but not intense enough to produce the same speed and power gains as higher zones. That doesn’t mean Zone 3 is useless. It’s a natural place to land during tempo workouts and race simulations. But spending too much time there at the expense of easy and hard days is one of the most common training mistakes.
If you’re newer to exercise, spending most of your time in Zones 1 and 2 builds your aerobic foundation while keeping injury risk low. As your fitness improves, you can add structured intervals in Zones 4 and 5 once or twice a week.
Signs You’re Overdoing It
Your resting heart rate is one of the simplest indicators of recovery. A resting rate that creeps several beats above your normal baseline for multiple days can signal that your body hasn’t recovered from recent training. In early stages of overtraining, resting heart rate often rises. In more advanced overtraining, the opposite can happen: resting heart rate drops unusually low, and performance declines even after rest. Other red flags include persistent fatigue, irritability, disrupted sleep, and a noticeable drop in your ability to hit the intensities that used to feel manageable.
Tracking your resting heart rate each morning gives you a personal trend line. A spike of five or more bpm that persists for several days is a reliable signal to pull back and prioritize recovery in Zones 1 and 2 before returning to harder efforts.