Heart Rate Zones
Five training zones from your maximum and resting heart rate, using the Karvonen reserve method or plain percentages — with a clear account of why the two disagree.
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Five training zones
Four max-HR formulas
Karvonen reserve method
Measured lying still, first thing in the morning, before you get up.
If you have ever seen a real maximum in a hard race or test, use it — it beats every formula.
How should the maximum be estimated?
Maximum heart rate
—
Heart rate reserve—
Resting heart rate—
Spread across the four formulas—
Fat-burn / easy zone—
Aerobic threshold (approx)—
MAF ceiling (180 − age)—
Training zones
Every formula, side by side
| Formula | Max HR | Zone 2 top | Zone 4 bottom | Notes |
|---|
Where the zones sit
Each bar is the width of that zone in beats per minute. The Karvonen method compresses the low zones and widens the top ones compared with plain percentages.
Instructions
How to use this calculator
Step by step
- Enter your age and resting heart rate. For the resting figure, take your pulse lying still first thing in the morning before you sit up, or read it off a watch that logs overnight — anything measured during the day is too high.
- If you have ever seen a genuine maximum — the highest number on your watch at the end of a hard race or a proper max test — put it in the third box. It overrides every formula, and it will usually differ from all of them by five or ten beats.
- Choose a formula if you are estimating. Tanaka is the sensible default; Gulati is the better fit for women; 220 − age is included because you will meet it constantly, not because it is accurate.
- Pick Karvonen or plain percentage for the zones. Karvonen uses your heart rate reserve and so accounts for your resting fitness, which is why the two methods disagree — the note under the zones explains what you are choosing between.
- Read the five zones. The description of each one matters more than its number: if you cannot speak in full sentences, you are not in zone 2, whatever the watch says.
- Use the comparison table to see how much the choice of formula actually moves your zone boundaries. If it moves them by less than you care about, stop worrying about which formula you picked.
Good to know
- Around 80% of your training time should be in zones 1 and 2, and most people find that far easier said than done. The polarised model is well supported and consistently ignored.
- Heart rate lags effort by a minute or two, drifts upwards in heat and dehydration, and runs several beats lower in the pool and on the bike than running. Use it as a guide, not a governor.
- Track resting heart rate over time. A sustained rise of five or more beats above your normal usually means fatigue, illness or under-recovery before you feel it.
- Chest straps are considerably more accurate than wrist optical sensors, particularly during intervals and in the cold. If your zones look wrong, suspect the sensor before the formula.
- A proper max HR test is genuinely unpleasant and should not be attempted if you have any cardiac risk factors. Taking the highest value from a hard race is safer and nearly as useful.
- Caffeine, stress, illness and poor sleep all shift heart rate for a given effort. On those days train by feel and ignore the numbers.
The maths behind it
- Tanaka HRmax = 208 − 0.7 × age Meta-analysis of 351 studies, 18,712 subjects. The current standard.
- Gellish HRmax = 207 − 0.7 × age Longitudinal data over 43 years; agrees closely with Tanaka.
- Fox HRmax = 220 − age The familiar one. Standard deviation around 12 bpm; no original data behind it.
- Gulati HRmax = 206 − 0.88 × age Derived from 5,437 women; the better choice for women.
- Heart rate reserve HRR = HRmax − HRrest The working range your training actually happens in.
- Karvonen zone target = HRrest + intensity × HRR Accounts for resting fitness; the preferred method.
- Percentage of maximum target = intensity × HRmax Simpler, ignores resting rate, sets easy zones lower.
- MAF ceiling 180 − age Maffetone's aerobic ceiling, adjusted up or down for training history and illness.
Why not just use 220 minus age?
Because it was never derived from data. It appeared in a 1971 paper as an informal fit to a scatter of published values, and its author later said it was not intended as a precise formula. It has a standard deviation of about 12 bpm, and it systematically overestimates the maximum in younger people and underestimates it in older ones. Tanaka is a small change to the arithmetic and a large improvement in accuracy.
What is the difference between Karvonen and percentage of maximum?
Karvonen takes percentages of your heart rate reserve — the gap between resting and maximum — and adds them to your resting rate. Percentage of maximum takes them straight off the maximum. For a fit person with a low resting rate the two methods can differ by fifteen beats in zone 2. Karvonen is the more meaningful of the two because it scales with your fitness.
Is there really a "fat burning zone"?
Sort of, and it matters much less than gym posters suggest. At low intensities a higher proportion of energy comes from fat, but the total energy burned is smaller. For fat loss the total matters more than the ratio, and the real argument for training easy is that it builds aerobic fitness without accumulating fatigue — not the fuel mix.
How do I find my true maximum heart rate?
The safest practical method is to take the highest reading from a hard race of 5–20 minutes, or a well-warmed-up session of three progressively harder hill repeats with the last one all-out. Do not attempt a maximal test if you have cardiac risk factors, are unwell, or have not been training. A supervised laboratory test is the proper answer.
Why is my heart rate lower on the bike than running?
Running uses more muscle mass and involves supporting your body weight, so heart rate runs roughly five to ten beats higher than cycling at the same perceived effort, and swimming is lower still. If you train in more than one sport, set zones separately for each rather than reusing your running numbers.
My heart rate climbs during a steady run even though the pace is constant. Is that a problem?
That is cardiac drift, and it is normal. As you lose fluid and core temperature rises, stroke volume falls and rate rises to compensate — commonly five to ten beats over an hour in the heat. It is worth watching as a hydration signal, not a reason to slow down every time it appears.
Do the zones change as I get fitter?
Your maximum barely moves with training — it is largely fixed by age and genetics and declines slowly. What changes is everything underneath it: your resting rate falls, your threshold moves to a higher percentage of maximum, and you go far faster at the same heart rate. That is why Karvonen zones, which use resting rate, shift as you improve and percentage-of-max zones do not.