To determine your heart rate zones, you need two numbers: your maximum heart rate and your resting heart rate. From there, you can use a simple formula to carve your full heart rate range into five training zones, each tied to a different intensity level and energy system. The method you choose depends on whether you want a quick estimate or a more personalized result.
Find Your Maximum Heart Rate
The simplest estimate is 220 minus your age. A 35-year-old would get a max of 185 beats per minute. This formula has been the standard for decades, but it paints with a broad brush. Studies comparing several age-based formulas to actual measured max heart rates found wide margins of error across all of them, with most equations overestimating max heart rate in people whose true max is lower and underestimating it in people whose true max is higher.
That said, the 220-minus-age formula is a reasonable starting point if you’re new to zone-based training. If your zones feel consistently too easy or too hard once you start using them, that’s a sign your true max differs from the estimate, and a field test will get you closer.
Measure Your Resting Heart Rate
Your resting heart rate is the second ingredient. Take it first thing in the morning, before you get out of bed, on three or four consecutive days, then average those readings. Most fitness watches will track this automatically overnight.
Several things can shift your resting heart rate from day to day. Alcohol, poor sleep, heat, caffeine, and even loud environmental noise all affect heart rate variability and baseline pulse. Illness, stress, and being significantly overweight push resting heart rate higher, while consistent aerobic training brings it down over time. For the most accurate baseline, measure on normal, well-rested mornings.
The Two Main Calculation Methods
Percentage of Max Heart Rate
The straightforward approach is to multiply your max heart rate by a percentage for each zone. The American Heart Association defines moderate exercise as 50% to 70% of max and vigorous exercise as 70% to 85% of max. Mapped across five zones, the ranges typically look like this:
- Zone 1 (50–60% of max): Warm-up, cooldown, recovery
- Zone 2 (60–70% of max): Easy endurance, fat burning
- Zone 3 (70–80% of max): Moderate effort, aerobic fitness
- Zone 4 (80–90% of max): Hard effort, speed and strength
- Zone 5 (90–100% of max): All-out, peak capacity
For a 35-year-old with a max of 185, Zone 2 would be roughly 111 to 130 bpm. This method is quick but ignores your fitness level entirely, since two people the same age can have very different resting heart rates.
Heart Rate Reserve (Karvonen Method)
The Karvonen method accounts for your fitness by factoring in resting heart rate. First, calculate your heart rate reserve: max heart rate minus resting heart rate. Then multiply that reserve by the zone percentage, and add your resting heart rate back.
Here’s how it works for a 35-year-old with a max of 185 and a resting heart rate of 60:
- Heart rate reserve: 185 − 60 = 125 bpm
- Zone 2 target (60–70%): (125 × 0.60) + 60 = 135 bpm on the low end, (125 × 0.70) + 60 = 148 bpm on the high end
Notice Zone 2 lands at 135 to 148 bpm here, compared to 111 to 130 using the simpler method. The Karvonen formula produces higher zone boundaries for fit individuals with low resting heart rates, which more accurately reflects where their body actually shifts between energy systems. If you’re serious about training by zones, this is the better formula to use.
Use a Field Test for Greater Accuracy
Formulas estimate. A field test measures. The most widely used protocol, popularized by endurance coach Joe Friel, finds your lactate threshold heart rate (the point where your body shifts from primarily aerobic to increasingly anaerobic effort) and anchors your zones to that real data point.
The test is simple but demanding. Warm up thoroughly, then run or ride as hard as you can sustain for 30 minutes, completely solo. Training partners or race settings will push your effort beyond what’s sustainable and skew the result. Go all out from the start. Don’t ease into it for the first 10 minutes and then ramp up. Don’t watch your heart rate during the effort; focus only on maintaining the hardest pace you can hold.
Ten minutes in, press the lap button on your watch. When the 30 minutes are done, look at your average heart rate for just the final 20 minutes. That number approximates your lactate threshold heart rate. Most training software and watches let you set custom zones based on this threshold, dividing your range into zones that reflect your actual physiology rather than an age-based guess.
What Each Zone Feels Like
Numbers on a watch are useful, but perceived effort is the reality check. Each zone has a distinct feel, and the simplest gauge is how well you can talk.
In Zone 1, conversation flows easily. Your breathing is relaxed, and the effort feels light. This is where warm-ups, cooldowns, and recovery sessions live. Your body burns almost exclusively fat for fuel at this intensity.
Zone 2 still feels manageable, but you’ll pause mid-sentence now and then to catch your breath. This is the classic “easy run” zone, and it’s where long, steady sessions build your aerobic engine. Fat remains the primary fuel source. Many coaches consider Zone 2 the most important zone for building a fitness base.
Zone 3 is where talking becomes minimal. Breathing intensifies, and the effort feels comfortably hard. Your body starts pulling from carbohydrates and protein alongside fat. This zone builds both strength and endurance but sits in a middle ground that can accumulate fatigue quickly if overused.
Zone 4 is genuinely hard. Speaking takes real effort, and you’re approaching your redline. The body relies heavily on carbohydrates for fuel here. Intervals in this zone develop speed and the ability to sustain high-intensity efforts.
Zone 5 is maximal. You’re gasping, not talking. These short bursts, usually lasting only seconds to a couple of minutes, force your heart to work at peak capacity and recruit fast-twitch muscle fibers. Nobody sustains Zone 5 for long.
The Talk Test as a Backup Method
If you don’t have a heart rate monitor, the talk test is a surprisingly reliable substitute. Research on trained cyclists found that the point where speaking first becomes uncomfortable corresponds closely to the ventilatory threshold, which falls around 80 to 85% of max heart rate. The point where speech becomes clearly impossible aligns with the respiratory compensation threshold, a higher marker near the top of Zone 4.
In practical terms: if you can speak in full sentences, you’re in Zones 1 or 2. If conversation is broken and strained, you’re in Zone 3. If you can only get out a few words, you’re in Zone 4. If talking is out of the question, you’ve hit Zone 5. This won’t give you exact beats per minute, but it’s a free, no-equipment way to stay in the right ballpark.
Getting Accurate Readings From Your Device
Chest strap monitors that detect electrical signals from the heart remain the gold standard for accuracy, especially during high-intensity intervals where your effort and movement change rapidly. Wrist-based optical sensors on smartwatches have improved significantly, but they can lag or misread during intense efforts, particularly when sweat loosens the band or wrist motion disrupts the sensor. If your zones matter for structured training, a chest strap during key workouts and tests will give you cleaner data.
Regardless of device, recalculate your zones every few months. As your fitness improves, your resting heart rate tends to drop and your lactate threshold shifts upward. Zones built on old numbers will eventually have you training at the wrong intensity. A quick retest of your resting heart rate, or a repeat of the 30-minute field test, keeps your zones calibrated to where your body actually is.