To figure out your heart rate zones, you need two numbers: your maximum heart rate and your resting heart rate. From there, simple math divides the range between them into five zones, each corresponding to a different level of exercise intensity. The whole process takes about five minutes once you have those starting numbers.
Find Your Resting Heart Rate First
Your resting heart rate is the baseline for accurate zone calculations. The best time to measure it is right when you wake up in the morning, before you get out of bed. Place your index and middle fingers on the inside of your wrist just below your thumb, or on the side of your neck next to your windpipe. Count the beats for 15 seconds and multiply by four to get your beats per minute.
Do this on three or four mornings and average the results. A single reading can be thrown off by poor sleep, stress, or dehydration. Most adults land somewhere between 60 and 100 beats per minute, with fitter individuals often in the 50s or lower. Wearable devices track resting heart rate automatically, but their accuracy varies by brand and model, so a manual check is worth doing at least once to verify.
Estimate Your Maximum Heart Rate
The classic formula is 220 minus your age. A 40-year-old would get a max of 180 beats per minute. It’s simple, widely used, and good enough for most people starting out. But this formula can be off by 10 to 12 beats per minute in either direction, which is enough to put you in the wrong zone.
A more refined formula, developed by researcher Tanaka, calculates max heart rate as 208 minus 0.7 times your age. For that same 40-year-old, the result is 180, essentially the same. But the two formulas diverge more at younger and older ages. A 25-year-old gets 195 from the classic formula but 190.5 from Tanaka’s. A 60-year-old gets 160 versus 166. Tanaka’s version tends to be more accurate for people over 40.
The only way to know your true maximum heart rate is through a graded exercise test, where you push to full effort under supervision (usually on a treadmill). If you’re training seriously or your calculated zones don’t feel right, that test is worth considering. For general fitness, the formulas work fine.
The Two Methods for Calculating Zones
Percentage of Max Heart Rate
The straightforward approach: multiply your max heart rate by the percentage range for each zone. If your max is 180, Zone 2 (60 to 70%) runs from 108 to 126 beats per minute. This method is fast and requires only one number. Its weakness is that it ignores your fitness level entirely. Two people who are both 35 will get identical zones even if one is a couch potato and the other runs marathons.
Heart Rate Reserve (Karvonen Method)
This method accounts for your fitness by factoring in resting heart rate. The formula uses your “heart rate reserve,” which is simply your max heart rate minus your resting heart rate. To find a target, you multiply your heart rate reserve by the desired percentage, then add your resting heart rate back.
Here’s a worked example for a 40-year-old with a resting heart rate of 65:
- Max heart rate: 220 minus 40 = 180
- Heart rate reserve: 180 minus 65 = 115
- Zone 2 lower bound (60%): 115 × 0.60 + 65 = 134
- Zone 2 upper bound (70%): 115 × 0.70 + 65 = 145.5
Notice how the Karvonen method gives a Zone 2 range of 134 to 146, compared to 108 to 126 using the simple percentage method. The Karvonen numbers better reflect actual effort because someone with a low resting heart rate has a wider working range. If you’re willing to do the extra math, this is the more accurate approach.
The Five Zones and What They Do
Heart rate zones are typically divided into five tiers, each as a percentage of your max heart rate (or heart rate reserve, if using the Karvonen method).
- Zone 1 (50 to 60%): Warm-up and recovery pace. Your body burns mostly fat at this intensity, but the overall calorie burn is low. This is the effort level of a casual walk. Use it for warm-ups, cool-downs, and active recovery days.
- Zone 2 (60 to 70%): Light aerobic effort. You can hold a full conversation comfortably. Your body still relies primarily on fat for fuel with minimal strain. This is the zone for building an endurance base, and it’s where most of your weekly training time should fall if you’re focused on long-term cardiovascular health.
- Zone 3 (70 to 80%): Moderate, tempo-pace effort. Conversation becomes choppy. Your body starts pulling from a mix of fat, carbohydrates, and protein. This zone builds both strength and endurance but accumulates more fatigue than Zone 2.
- Zone 4 (80 to 90%): Hard effort near your lactate threshold. You can only manage a few words at a time. Your body shifts to burning mostly carbohydrates. Training here improves speed and the ability to sustain high-intensity effort.
- Zone 5 (90 to 100%): All-out, maximum effort. You can sustain this for only a minute or two. It builds peak cardiac output and fast-twitch muscle fibers but demands significant recovery time afterward.
Why Zone 2 Gets So Much Attention
Zone 2 has become the most talked-about zone in fitness circles, and there’s a practical reason: it’s the highest intensity where your body still runs primarily on fat, with minimal glycogen depletion and low metabolic stress. Blood lactate stays between roughly 1.5 and 2.0 millimoles per liter, just below the threshold where effort starts to feel distinctly harder. A 10-week study in people with type 2 diabetes found that training at this intensity increased mitochondrial enzyme activity, meaning cells became better at producing energy.
That said, the benefits of Zone 2 are sometimes overstated. Meta-analyses show that low-intensity exercise produces more modest improvements in mitochondrial function compared to higher-intensity work. The real advantage of Zone 2 is that you can do a lot of it. It’s gentle enough to repeat daily without accumulating injury risk or excessive fatigue, so it builds a large aerobic base over time. The sweet spot for most people is spending roughly 80% of training time in Zones 1 and 2, with the remaining 20% in Zones 3 through 5.
Checking Your Zones Without a Monitor
If you don’t have a heart rate monitor, the talk test is a surprisingly reliable way to gauge intensity. During moderate effort (Zones 2 and 3), you can talk but not sing. During vigorous effort (Zone 4 and above), you can only get out a few words before needing a breath. If you can sing along to music, you’re in Zone 1.
The CDC also recommends a simple 0-to-10 effort scale. Moderate activity feels like a 5 or 6. Vigorous activity starts at 7 or 8. These subjective tools are especially useful if you take beta blockers or other medications that lower your heart rate, since the formulas will overestimate the effort needed to reach a given number. In that case, perceived effort is a more trustworthy guide than any heart rate target.
Wrist Monitors vs. Chest Straps
If you do want to track your zones with a device, accuracy depends on what you’re wearing and what you’re doing. Chest strap monitors are the gold standard for real-time heart rate tracking. Wrist-based optical sensors (the kind built into most smartwatches) perform well during jogging and arm-based exercises but can underread significantly during cycling. One study found wrist monitors recorded averages around 105 to 106 beats per minute on a stationary bike, while the chest strap read 127 for the same effort. That’s a difference large enough to place you in the wrong zone entirely.
The issue is motion artifact. Wrist sensors use light to detect blood flow through the skin, and gripping handlebars or absorbing vibration can interfere with the reading. For walking and running, wrist devices are generally reliable enough. If you cycle regularly or want precision across all activities, a chest strap paired with your watch will give you more dependable numbers to train from.
Putting Your Zones Into Practice
Once you’ve calculated your ranges, the simplest way to use them is to assign a zone to each workout before you start. An easy 45-minute jog stays in Zone 2. A tempo run targets Zone 3. Intervals alternate between Zone 4 or 5 during the work period and Zone 1 or 2 during rest. Having specific numbers turns vague instructions like “go easy” into something measurable.
Recalculate your zones every six months or so, or whenever your resting heart rate changes meaningfully. As your fitness improves, your resting heart rate typically drops, which shifts your Karvonen-based zones upward. Your max heart rate also decreases slightly with age, roughly 0.7 beats per year. Neither change is dramatic in the short term, but over a year or two the numbers can drift enough to matter.