Heart rate zone calculator

Heart rate zones give you a number range to aim for, so you're not guessing whether a run, ride or brisk walk is "easy" or "hard." That makes it easier to keep easy days truly easy and hard days purposeful.

How the zones are calculated

1. Estimate max heart rate. The Tanaka formula, 208 − 0.7 × age, is the default. You can switch to 220 − age, or enter a max you've actually measured during a hard effort.
2. Find your heart rate reserve. If you enter a resting heart rate, the calculator uses the Karvonen method: reserve = max − resting.
3. Set the zones. Zone limits are 50, 60, 70, 80, 90 and 100% of your reserve, added back to your resting rate. Without a resting rate, the percentages apply to max heart rate directly.

Worked example

A 40-year-old with a resting heart rate of 60: max ≈ 208 − 0.7 × 40 = 180 bpm. Reserve = 180 − 60 = 120. Zone 2 (60–70%) = 60 + 120 × 0.6 to 60 + 120 × 0.7 = 132–144 bpm.

Without the resting heart rate, zone 2 would simply be 60–70% of 180, or 108–126 bpm. The Karvonen version comes out higher because it starts from your resting rate. Neither is wrong, but if you know your resting heart rate, the Karvonen zones are usually a better personal fit.

What each zone feels like and what it's for

• Zone 1 (50–60%): very easy. Brisk walking or a very gentle jog or spin. You can talk in full sentences without effort. Good for warm-ups, cool-downs and recovery days.
• Zone 2 (60–70%): easy. Breathing is a little deeper, but you can still hold a conversation. This is where many endurance plans put most of their training, because you can sustain it for a long time and recover from it quickly.
• Zone 3 (70–80%): moderate. You can talk, but only in shorter sentences. It feels like steady, purposeful work.
• Zone 4 (80–90%): hard. You can only say a few words at a time. Used for tempo efforts and intervals lasting several minutes.
• Zone 5 (90–100%): very hard. Talking isn't really possible. Used only for short intervals, and best kept for people who already exercise regularly and have no health concerns.

The talk test as a backup

Your breathing is a reliable check that doesn't depend on a formula or a gadget. If you can talk comfortably in full sentences, you're working easily. If you can manage only short phrases, you're working moderately hard to hard. If you can barely get a word out, you're working very hard. When the number on your watch and the talk test disagree, go with the talk test.

Heart rate also lags behind effort, often taking a minute or more to climb at the start of an interval, so judge short efforts by feel. On long sessions or hot days it tends to drift upward at the same pace.

How to measure your resting heart rate

1. Measure in the morning right after you wake up, before you get out of bed and before any coffee.
2. Lie still for a minute. Then find your pulse on the thumb side of your inner wrist, using two fingers rather than your thumb.
3. Count the beats for a full 60 seconds, or count for 30 seconds and double it.
4. Repeat on three to five mornings and use the average.

Poor sleep, alcohol, caffeine, stress, heat, illness and a hard workout the day before can all push resting heart rate up for a while. For most adults, a resting heart rate between 60 and 100 bpm is considered normal, and regular exercisers are often lower. If yours is regularly above 100, unusually low and you feel dizzy or tired, or your heartbeat often feels irregular or racing, mention it to a doctor.

Why the formulas can be off for you

Max heart rate formulas are built from averages across many people. Two healthy 40-year-olds can have max heart rates 20 beats apart, and neither is better or fitter because of it. Max heart rate mostly reflects age and genetics, and it doesn't change much with training.

A few signs your estimated zones don't fit you:

• Zone 2 feels hard and you can't hold a conversation. Your real max may be lower than the estimate.
• You can chat easily near the top of zone 4. Your real max may be higher than the estimate.

The highest heart rate you've seen during a recent race or hard interval session gives you a rough floor: your true max is at least that high. An all-out max test isn't a good idea for beginners or anyone with health concerns. If you want a measured number, a supervised exercise test with a doctor or sports clinic is the safest way to get one.

Wrist sensors vs chest straps

Most watches and fitness bands use an optical sensor that shines light into your skin to detect blood flow. They're often reasonably accurate during steady exercise, but can lag or misread during intervals, weightlifting, cold weather, or when the band is loose. Some even lock onto your running cadence.

Chest straps read the heart's electrical signal directly, so they tend to be more accurate and respond faster. If you use a wrist device, wear it snug and a finger's width above your wrist bone. Be skeptical of sudden spikes that don't match how you feel.

Mixing easy and hard training across a week

Many endurance plans keep most training easy, in zones 1–2, and a smaller share hard, in zones 4–5. Easy sessions build your aerobic base and can be repeated often without much fatigue. Hard sessions take more out of you and need recovery around them.

For someone doing cardio four times a week, a simple pattern could be three easy zone 2 sessions and one session with intervals or a steady zone 3–4 effort. Avoid two hard days in a row. If you're new to exercise, keep everything easy for the first several weeks before adding harder work.

Public health guidelines recommend that adults get at least 150 minutes of moderate activity or 75 minutes of vigorous activity per week, plus muscle-strengthening work on two or more days. Moderate effort roughly lines up with zones 2–3 and vigorous effort with zones 4–5. More detail is in how much exercise you need per week. If running is your sport, see how to start running and running pace and race goals.

Limits worth knowing

• Formulas estimate the average. Your real max can be 10–20 bpm higher or lower. If your zones feel wrong, trust your breathing and the "talk test".
• Wrist sensors vary. Optical heart rate is less accurate during intervals than a chest strap.
• Medication matters. Beta-blockers and some other medicines lower heart rate, which makes these zones misleading. Ask your doctor for safe ranges.
• Conditions change the picture. If you have a heart condition, have had chest pain or fainting, are pregnant, or are new to exercise with risk factors such as high blood pressure or diabetes, talk to a doctor before starting vigorous training. They may give you a personal target range.
• Know when to stop. Stop exercising if you feel chest pain or pressure, unusual shortness of breath, dizziness, or a pounding or irregular heartbeat. If it doesn't settle quickly with rest, get emergency help.

For what each zone is good for, and how to use easy zone 2 training, read heart rate zones explained. For pace-based planning, use the running pace calculator.

Based on: Tanaka (2001) max heart rate formula and the Karvonen method (1957).