Heart rate zone calculator
Training zones by both of the methods called “heart rate zones”, and the distance between them — which is exactly your resting rate times how far below maximum you are working, so it is widest at the easy end and vanishes at the top. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
The difference is your resting heart rate, times the shortfall
Two things are called heart rate zones:
- Percentage of maximum: HRmax × p
- Karvonen, on heart rate reserve: (HRmax − HRrest) × p + HRrest
Expand the second and it becomes HRmax × p + HRrest × (1 − p), so the difference between them is exactly
HRrest × (1 − p)
Three things follow, and none of them needs a study. Karvonen is always the higher of the two, never the lower. The gap does not depend on your maximum at all. And it is widest at the easy end, closing steadily to nothing as you approach maximum.
They agree exactly at maximum, which is why nobody notices
Put p = 1 into HRrest × (1 − p) and the difference is zero. Not approximately: exactly, for everybody, whatever their resting heart rate.
So the one value where the two methods cannot disagree is the one value somebody comparing them would naturally reach for. This site has run into that shape twice before — two candidate formulas for API gravity agree at exactly 10°, which is the figure every textbook names as the sanity check, and “220 minus age” agrees with Tanaka at exactly age 40.
The rule each time: check where the candidates diverge most, not where the arithmetic is prettiest. Memorable values are usually memorable because they are degenerate.
The gap is widest where beginners are sent
At the bottom of the easiest zone, p = 0.5, the difference is half your resting heart rate — 30 bpm for a resting rate of 60.
That is the zone most often prescribed to somebody starting out, coming back from injury, or in cardiac rehabilitation. The place where the method matters most is the place where the people least able to tell are sent.
And because the gap is proportional to resting heart rate, it is largest in beats for the least fit — 40 bpm at a resting rate of 80, against 22.5 for an endurance athlete at 45. That runs opposite to the usual claim that Karvonen matters more for athletes.
Which means the zone names disagree
For a 40-year-old with a resting rate of 60, Karvonen’s “very light” zone starts at 120 bpm — a heart rate the percentage method calls “light”. Karvonen’s “moderate” starts where the percentage method says “hard”. In three of the five zones the two ranges do not overlap at all.
Told to train in a zone by name, you are being sent to different heart rates depending on which method whoever told you was using — and neither of them will have said which.
Both are applied to an estimate
Unless you have had your maximum measured in a laboratory, it came from a formula. An age-predicted HRmax has an individual spread of about ±10 bpm, which is wider than the gap between the two methods in the top two zones.
So in the hard zones the argument about method is smaller than the uncertainty about the number both methods start from — and in the easy zones it is not. Which of the two problems dominates depends on where you are training, and no page that prints a single target to the nearest beat is in a position to say.
What this is not
It is not a training plan and it does not prescribe a zone. The five-zone scheme is a convention: schemes with three zones and with seven are both in use, and no boundary in any of them was derived from a measurement of anybody.
The zone commonly labelled “fat burning” is shown here under its percentage, because the label is a claim about substrate use that this page has no way to compute and does not make.
Karvonen, M. J., Kentala, E., & Mustala, O. (1957). “The effects of training on heart rate: a longitudinal study.” Annales Medicinae Experimentalis et Biologiae Fenniae 35: 307–315. · Maximum heart rate from Tanaka, H., Monahan, K. D., & Seals, D. R. (2001), by way of this site’s own maximum heart rate page, which is where the ±10 comes from.