About the Target Heart Rate Calculator
A target heart rate is always a percentage of something, and most of the confusion around training zones comes from charts that do not say what.
There are two methods in common use, and they are not interchangeable.
Percent of maximum multiplies your maximum heart rate by a percentage. It needs only an age.
Karvonen works on your heart rate reserve — maximum minus resting — and adds your resting rate back on top. It needs a resting rate as well, and in return it reflects how fit you are.
At the same percentage, the two give different answers, so each comes with its own set of percentages. This target heart rate calculator keeps them apart, shows the working for whichever you choose, and makes the weakest part of both — the estimated maximum — visible rather than buried.
How to Use the Target Heart Rate Calculator
Enter your age and choose a method. Karvonen is the default and the better choice if you know your resting heart rate; measure it first thing in the morning before getting up.
Choose how to set your maximum heart rate: one of three age formulas, or a measured maximum if you have one from an exercise test.
Pick an intensity — moderate, vigorous, or a custom range of percentages.
How the Two Methods Work
Percent of maximum: target = % × maximum
Karvonen: target = resting + % × (maximum − resting)The standard bands differ between them:
| Intensity | % of maximum (AHA) | % of reserve (ACSM) |
|---|---|---|
| Moderate | 50 to 70% | 40 to 59% |
| Vigorous | 70 to 85% | 60 to 89% |
Mixing a Karvonen formula with percent-of-maximum percentages, or the other way round, is the most common reason two charts disagree.
Step-by-Step Example
Age 40. Resting heart rate 65. Karvonen, moderate intensity.
Maximum: 208 − 0.7 × 40 = 180 bpm
Reserve: 180 − 65 = 115 bpm
Lower target: 65 + 40% × 115 = 111 bpm
Upper target: 65 + 59% × 115 = 133 bpmSo moderate exercise is about 111 to 133 beats per minute, and the vigorous band runs from about 134 to 167.
To check it mid-session, divide by six: 19 to 22 beats in a 10-second count.
Why Karvonen Comes Out Higher
At the same percentage, Karvonen always gives the higher number, and the gap has a tidy form:
Karvonen − % of max = resting × (1 − %)At 70% with a resting rate of 60, that is 60 × 0.3 = 18 beats per minute.
The reason is that Karvonen never lets the target fall below your resting rate: 0% of reserve is your resting rate, not zero. That is also why it tracks fitness. Two 40-year-olds with the same maximum but resting rates of 50 and 80 get different moderate zones, which is what you would want — the fitter one has more room between resting and maximum.
The Weak Link: Your Maximum
Both methods rest on a maximum heart rate, and for most people that maximum is estimated from age.
220 − age is the best known formula and the least well founded. It is usually traced to Fox and Haskell in 1971, who drew a line through roughly ten published data sets. It was never presented as a formula for individuals.
Tanaka (2001), 208 − 0.7 × age, came from a meta-analysis of 351 studies and more than 18,000 people, then confirmed in a laboratory study. It is the default here.
The two agree at exactly one age:
220 − a = 208 − 0.7a → 0.3a = 12 → a = 40Below 40, 220 − age runs high; above it, low. At 70 it is about 9 beats under.
Gellish (2007), 207 − 0.7 × age, came from following the same people over years and lands within a beat of Tanaka.
More important than which formula you pick: any of them is only good to about 10 beats either side for an individual. Two people of the same age can differ by 20 beats or more. A measured maximum, from a supervised exercise test, replaces the estimate entirely.
When the Numbers Feel Wrong
Because the maximum is an estimate, the zone can be off for you in particular. The talk test is a useful cross-check that needs no arithmetic:
Moderate — you can talk in full sentences, but not sing.
Vigorous — you can only get a few words out between breaths.
If the calculated zone and the talk test disagree consistently, trust the talk test, or get your maximum measured.
Understanding Your Result
Target heart rate is the range for the intensity you chose.
How it was worked out names the method, the percentages and the maximum used.
Both zones gives moderate and vigorous ranges side by side, labelled with their source.
Checking it mid-session converts the range into a 10-second pulse count.
Worth knowing compares formulas, or explains how to make the zone more personal.
When Should You Use This Calculator?
When starting a structured exercise plan that specifies moderate or vigorous intensity.
To set up a heart rate monitor or watch with zones based on your own resting rate rather than defaults.
After your resting rate changes, since every Karvonen zone moves with it.
Not as a safety limit. If you have a heart condition or take medicines that affect heart rate, such as beta blockers, age-based zones may not apply at all.
Common Mistakes
Mixing methods and percentages. 70% of maximum and 70% of reserve are different targets.
Treating 220 − age as precise. It was never derived for individuals.
Using a daytime resting rate. Measure it on waking.
Chasing a "fat-burning zone". Total energy spent matters more than the fuel mix for weight loss.
Counting your pulse for a full minute during exercise. It falls while you count; ten seconds is better.
Check with a doctor before starting vigorous exercise if you have a heart condition, chest pain on exertion, or have been inactive for a long time. Nothing here is medical advice.