Karvonen Formula Calculator

The Karvonen formula builds target heart rates from heart rate reserve — the gap between your resting and maximum pulse — instead of from maximum alone. The arithmetic is target = (reserve × intensity) + resting. Enter your age and your resting heart rate and the calculator applies it to all five zones.

The arithmetic, one step at a time

Someone 30 years old with a resting pulse of 60 bpm, aiming at 70% intensity:

1. Maximum heart rate = 220 − 30 = 190 bpm
2. Heart rate reserve = 190 − 60 = 130 bpm
3. 70% of the reserve = 130 × 0.70 = 91 bpm
4. Target = 91 + 60 = 151 bpm

Notice that resting heart rate is used twice: it shrinks the reserve, then gets added back at the end. The addition wins. Plain 70% of maximum for this person would be 133 bpm — eighteen beats lower than the Karvonen answer. Every Karvonen zone sits above its percent-of-maximum namesake, which is the single most common source of confusion when two people compare “zone 3”.

Why the resting pulse is doing the work

Resting heart rate is the one input here that describes you rather than your birthday. Take two 30-year-olds, one resting at 50 and one at 75:

	Resting 50	Resting 75
Reserve (max 190)	140 bpm	115 bpm
Target at 60%	134 bpm	144 bpm
Target at 80%	162 bpm	167 bpm

The fitter heart, with more room between rest and ceiling, gets a lower target at easy intensities and a wider spread across the range. That matches how the two people would actually feel at the same bpm, which is the whole argument for the method.

What Karvonen does not fix is the ceiling itself. Step 1 above is still 220 − age, still an estimate with roughly 10 to 12 bpm of scatter, and Tanaka’s meta-analysis showed the classic version reads low in older adults — swap in 208 − 0.7 × age and every zone below shifts with it. Personalizing the bottom of the range does nothing about uncertainty at the top.

Measuring the resting rate properly

A Karvonen zone is only as good as the resting number you feed it, and resting heart rate is easily distorted:

• Measure lying down, first thing, before getting out of bed, before coffee, before your phone.
• Count for a full 60 seconds, or for 30 and double it.
• Repeat across three or four mornings and take the average. A single reading can be inflated by a short night, yesterday’s caffeine, a warm room or an approaching cold.

A wearable that samples overnight will usually give a lower and steadier figure than a manual morning count, so pick one method and stay with it rather than mixing the two.

When plain percentages are the better tool

If you do not have a trustworthy resting number, do not guess one — a resting rate that is 10 bpm too high pushes every target up by several beats and makes easy sessions harder than intended. In that case the simpler heart rate zone calculator with percent of maximum is the more honest instrument, and the max heart rate calculator explains what it is built on.

This content is informational and does not replace guidance from an exercise professional.