Heart rate zones are five training bands set as percentages of your maximum heart rate or, better, your heart rate reserve. Zone 1 and 2 build aerobic fitness at an easy effort, zone 3 is moderate, and zones 4 and 5 train threshold and top-end speed. Most endurance athletes spend about 80% of their time in zones 1 and 2.
To use heart rate zones you need two numbers: your maximum heart rate and your resting heart rate. The heart rate zones calculator takes both and gives you all five zones in beats per minute. Below you will see how those numbers are worked out, why the popular 220 minus age formula can be well off for you, what each zone actually trains, and how to build a week around them.
Step 1: Estimate your maximum heart rate
Maximum heart rate (HRmax) is the highest rate your heart can reach during all-out effort. It falls with age, has little to do with fitness, and varies a lot between people of the same age. Several formulas estimate it:
| Formula | Equation | Result at age 50 |
|---|---|---|
| Fox | 220 − age | 170 bpm |
| Tanaka | 208 − 0.7 × age | 173 bpm |
| Gellish | 206.9 − 0.67 × age | 173 bpm |
| Inbar | 205.8 − 0.685 × age | 172 bpm |
| Nes | 211 − 0.64 × age | 179 bpm |
| Gulati (women) | 206 − 0.88 × age | 162 bpm |
The classic 220 minus age formula was never derived from a proper study and tends to overestimate max heart rate in young people and underestimate it in older people. The Tanaka formula, built from a large meta-analysis, is a better default for adults. The two agree at age 40 (180 bpm) and drift apart either side: at 20, Fox gives 200 and Tanaka 194, while at 60 Fox gives 160 and Tanaka 166. You can compare all six for your age with the maximum heart rate calculator.
Even the best formula is an average. Real max heart rates scatter by around 10 bpm either side of the prediction, so a 50-year-old could genuinely top out at 160 or at 185. If your zones feel wrong, that is usually why.
Testing your max heart rate
If you are healthy and already exercise regularly, a field test gives a far better number. After a thorough 15-minute warm-up, run or cycle hard uphill for three minutes, recover for two, then go again as hard as you can for three minutes, finishing with an all-out final 30 seconds. The highest reading on a chest strap is close to your true max. Skip this if you are new to exercise, have heart symptoms or take medicine that affects heart rate, and check with your doctor first.
Step 2: Measure your resting heart rate
Take your pulse first thing in the morning, before you get out of bed, for 60 seconds (or 15 seconds times 4). Do it on three to five mornings and average the results. A normal adult resting heart rate is 60 to 100 bpm, and trained endurance athletes often sit between 40 and 60. The heart rate calculator converts a 15-second count and rates the result.
Resting heart rate is also a handy recovery signal. If yours is 5 to 7 bpm above your normal average for a couple of mornings, you may be tired, getting ill, dehydrated or short on sleep. That is a good day for an easy session.
Step 3: Use the Karvonen method (heart rate reserve)
There are two ways to turn max heart rate into zones. The simple way takes a percentage of max: 70% of 173 is 121 bpm. The Karvonen method uses your heart rate reserve (HRR), the range between resting and max, and adds the resting rate back on:
Target HR = resting HR + intensity × (max HR − resting HR)
Karvonen is better because it accounts for fitness. Two people with the same max can have resting rates of 50 and 80, and the same percentage of max means a very different effort for each. The American Heart Association describes moderate exercise as roughly 50 to 70% of maximum and vigorous as 70 to 85%, but heart rate reserve percentages line up more closely with how hard an effort feels and with oxygen use. The Karvonen formula calculator gives a target for any intensity you choose.
Heart rate zones: a worked example
Take a 50-year-old with a resting heart rate of 60 bpm. Using Tanaka, max HR = 208 − 0.7 × 50 = 173 bpm. Heart rate reserve = 173 − 60 = 113 bpm.
Zone 2 lower limit with Karvonen: 60 + 0.60 × 113 = 127.8, so 128 bpm. Upper limit: 60 + 0.70 × 113 = 139.1, so 139 bpm. Here are all five zones both ways:
| Zone | Intensity | Karvonen (bpm) | % of max only (bpm) | How it feels |
|---|---|---|---|---|
| 1. Very light | 50 to 60% | 117 to 128 | 87 to 104 | Brisk walk, easy spin |
| 2. Light (aerobic base) | 60 to 70% | 128 to 139 | 104 to 121 | Easy, can talk in full sentences |
| 3. Moderate (tempo) | 70 to 80% | 139 to 150 | 121 to 138 | Comfortably hard, short sentences |
| 4. Hard (threshold) | 80 to 90% | 150 to 162 | 138 to 156 | A few words at a time |
| 5. Maximum | 90 to 100% | 162 to 173 | 156 to 173 | All-out, sustainable for minutes |
Notice how much lower the percentage-of-max zones are at the bottom end. For this person, 104 bpm is barely more than a stroll, yet the simple method calls it the start of zone 2. That gap is why the Karvonen numbers usually match perceived effort better for fit people with low resting rates.
What each zone trains
Zone 1: recovery
Very easy movement that improves blood flow without adding fatigue. Use it for warm-ups, cool-downs and recovery days after hard sessions.
Zone 2: aerobic base
The workhorse zone. Long, easy sessions here grow the number and size of your mitochondria, build capillaries in your muscles and teach your body to use fat as fuel. This is the so-called fat-burning zone, which the fat burning zone calculator works out three ways. Total calories burned, not the fuel mix during exercise, decide fat loss over weeks. The guide on how many calories you should eat covers that side.
Zone 3: tempo
Steady, comfortably hard running or riding. Useful for marathon-pace work, but easy to drift into on every run, which leaves you too tired for the hard days and not rested enough on the easy ones. Coaches call this the grey zone.
Zone 4: threshold
Around your lactate threshold, the effort you could hold for about an hour in a race. Intervals like 3 × 10 minutes in zone 4 raise the pace you can sustain. The anaerobic threshold calculator estimates this point at about 85% of max.
Zone 5: VO2 max and speed
Short, very hard efforts of 30 seconds to 5 minutes. They push your maximal oxygen uptake, the ceiling of your aerobic engine, which you can estimate with the VO2 max calculator. Heart rate lags behind effort here, so for short reps use pace or power and let heart rate confirm afterwards.
The 80/20 rule: how to split your week
Studies of elite endurance athletes by exercise physiologist Stephen Seiler and others found a consistent pattern: roughly 80% of training sessions at low intensity (zones 1 and 2) and 20% at high intensity (zones 4 and 5), with little time in zone 3. Recreational athletes who copy this pattern tend to improve more than those who train moderately hard every day.
For someone training five hours a week, that is about 4 hours (240 minutes) easy and 1 hour (60 minutes) hard. A sample week:
- Monday: rest or 30 minutes zone 1
- Tuesday: 60 minutes with 5 × 4 minutes in zone 4 to 5
- Wednesday: 50 minutes zone 2
- Thursday: 45 minutes zone 2
- Friday: rest
- Saturday: 60 minutes with 3 × 8 minutes in zone 4
- Sunday: 90 minutes zone 2 long session
Runners can pair this with pace targets; the guide to running pace shows how to turn a recent race into easy and tempo paces.
How to measure heart rate during exercise
- Chest strap: the most accurate option for training, close to an ECG. Best for intervals.
- Wrist optical sensor: fine for steady efforts, but often lags or jumps during intervals and can lock onto your running cadence. Wear it snug, two fingers above the wrist bone.
- Arm band optical sensor: more stable than the wrist, a good middle ground.
- Manual pulse: count for 15 seconds right after stopping and multiply by 4. It drops quickly, so it reads a little low.
Heart rate also drifts upward during long sessions in heat, as you lose fluid and your body sends more blood to the skin. A 10 bpm rise over an hour at the same pace is normal. Caffeine, stress, poor sleep and altitude push it up too, while beta blockers push it down, so treat zones as a guide alongside how the effort feels. The Mayo Clinic’s guide to exercise intensity covers the talk test and perceived exertion as cross-checks. This is general information, not personal medical advice, so speak to your doctor before hard training if you have a heart condition or take heart medicine.
Common mistakes
- Trusting 220 minus age blindly. If zone 4 feels easy or zone 2 feels like a struggle, your real max is probably different. Test it or use the Tanaka formula.
- Doing every session in zone 3. Moderate every day feels productive but leaves you tired and slow to improve.
- Chasing heart rate in short intervals. In a 1-minute rep heart rate may never reach zone 5. Judge short efforts by pace or feel.
- Forgetting to update zones. As fitness improves, resting heart rate falls and your Karvonen zones shift. Recalculate every couple of months.
- Using running zones on the bike. Max heart rate on a bike is often 5 to 10 bpm lower than running. Test each sport separately if you do both.
Frequently asked questions
What are the 5 heart rate zones?
Zone 1 (50 to 60%) is recovery, zone 2 (60 to 70%) builds aerobic base, zone 3 (70 to 80%) is tempo, zone 4 (80 to 90%) is threshold and zone 5 (90 to 100%) is maximal effort. The percentages apply to heart rate reserve with the Karvonen method or to max heart rate with the simple method.
What heart rate zone burns the most fat?
Zone 2 burns the highest share of fat, but harder zones burn more total calories per minute. For fat loss, total weekly energy balance matters far more than the zone.
How do I know my zone 2 heart rate?
With Karvonen it is resting HR plus 60 to 70% of your heart rate reserve. A practical check: you can breathe through your nose and speak in full sentences. For a 50-year-old with a resting rate of 60, it is about 128 to 139 bpm.
Is it dangerous to train in zone 5?
For healthy, trained people short zone 5 efforts are safe and useful. If you are new to exercise, older with risk factors or have any heart symptoms, get medical clearance before doing maximal work.
How much time should I spend in each zone?
A good default is about 80% of training time in zones 1 and 2 and 20% in zones 4 and 5, with only occasional zone 3 work, unless you are training specifically for a marathon-pace effort.
Why is my heart rate higher than usual on an easy run?
Heat, dehydration, poor sleep, stress, caffeine, illness or accumulated fatigue all raise heart rate at a given pace. If it stays high for several days, back off and recover.
Heart rate zones work best when they are built on your numbers, not on a formula you found on a gym poster. Measure your resting rate, pick a better max heart rate estimate or test it, plug both into the calculator and keep most of your training easy. After a few weeks, check your heart rate recovery after a hard effort: a faster drop is one of the clearest signs your fitness is improving. If you are also tracking body composition, the guide to BMI vs body fat percentage explains which number to watch.