Heart Rate Zone Calculator
Age and resting pulse in, five training zones out — with the effort each one buys.
| Zone | Beats per minute | What it trains |
|---|
Estimates for training planning, not medical guidance.
Two ways to draw the same five zones
Percentage of maximum is the simpler method: take your estimated max and slice it at 50, 60, 70, 80 and 90 percent. Karvonen instead works from heart rate reserve — the span between resting and maximum — and adds each percentage of that span back onto your resting rate. The two agree at the top end and diverge sharply at the bottom, which is exactly where most training time is spent.
Worked example: same age, different fitness
Two 35-year-olds share an estimated max of 185. One has a resting rate of 50, the other 75. By percentage of max, both get a zone 2 of 111 to 130. By Karvonen, the first gets 131 to 145 and the second 141 to 152. The fitter athlete's easy pace sits lower relative to their reserve, and the plain percentage method would have them training too easy to build anything.
What each zone is for
| Zone | Reserve % | Typical session |
|---|---|---|
| 1 Recovery | 50-60 | Warm-up, cool-down, day after a hard session |
| 2 Endurance | 60-70 | Long easy runs and rides, the bulk of weekly volume |
| 3 Tempo | 70-80 | Steady efforts, marathon-ish pace |
| 4 Threshold | 80-90 | Cruise intervals, 8 to 20 minute repeats |
| 5 Maximum | 90-100 | Short VO2 max intervals, 30 seconds to 5 minutes |
Measuring the inputs properly
Resting heart rate means truly resting: measured lying down, before getting out of bed, ideally averaged over several mornings. A reading taken at your desk after coffee can be 10 beats high, which shifts every zone boundary upward and makes easy days harder than intended.
Maximum heart rate is worth measuring rather than estimating if you train seriously. The 220-minus-age formula is a population average that misses individuals by 20 beats in either direction, and its error propagates into all five zones. A hard hill repeat session or a maximal race effort with a chest strap gives a much better anchor than a wrist optical sensor, which tends to lag and drop out at high intensity.
Treat the numbers as a guide rather than a rule. Heat, altitude, caffeine, illness and poor sleep all move heart rate for a given effort, sometimes by ten beats. On those days perceived exertion is the more honest signal — and if your heart rate behaves strangely at rest or during easy work, that is a question for a clinician, not a calculator.
Sources & further reading
- American Heart Association — target heart rate ranges and physical activity guidance
- CDC Physical Activity Basics — measuring exercise intensity and weekly activity targets
- American College of Sports Medicine — exercise testing and intensity prescription standards
- World Health Organization — physical activity recommendations by age group
Frequently asked questions
What is the Karvonen method and why use it?
Karvonen works from heart rate reserve — max minus resting — instead of max alone. Target = resting + (reserve x intensity). It accounts for how fit you are: two people the same age with resting rates of 45 and 75 get noticeably different zone boundaries, which the plain percentage-of-max method misses.
How accurate is the 220 minus age estimate?
It is a population average with a standard deviation of about 10 to 12 beats, so your true max can sit 20 beats either side. If you know your max from a lab test or a hard race with a chest strap, enter it — the zones shift accordingly and become far more useful.
How much time should I spend in each zone?
A common endurance split is roughly 80 percent of training time in zones 1 to 2 and 20 percent in zones 4 to 5, with zone 3 used sparingly. Easy days that drift into zone 3 are the classic mistake: too hard to recover from, too easy to drive adaptation.