Fitness & Sports

Target Heart Rate Calculator

What this does

Compute Karvonen training zones from your age and resting heart rate, with HRmax estimated by the Tanaka equation.

Enter your details

Runs in your browser

Calculator inputs

Measure first thing in the morning before rising.

How to use it

Using the target heart rate calculator

  1. 01

    Measure resting HR

    Count pulses for a full minute upon waking, or read it from a wearable’s overnight average.

  2. 02

    Enter age and pick intensity

    Age feeds the Tanaka maximum; the selector highlights your working zone in the table.

  3. 03

    Train by feel cross-check

    Zones should match breathing: easy zones allow full conversation, threshold work allows only short phrases.

Good to know

Why 208 − 0.7 × age beats 220 − age

Tanaka, Monahan & Seals pooled hundreds of laboratory-measured maxima and found the old 220 rule systematically overshoots for younger adults and undershoots older ones. Their regression halves the typical prediction error and never goes negative.

What heart-rate reserve adds

Two 40-year-olds share an HRmax estimate but might have resting rates of 45 versus 75. Percentage-of-max zones would hand them identical targets; Karvonen correctly assigns the trained athlete higher absolute training beats.

Zone cheat sheet

  • 50–60%: recovery, fat-oxidation base, fully conversational.
  • 70%: steady aerobic work, marathon-effort territory.
  • 85%: threshold; sustainable about an hour, phrases only.

How it's calculated

The math behind this calculator

HRmax = 208 − 0.7 × age (Tanaka) THR = (HRmax − HRrest) × %intensity + HRrest

Maximum heart rate comes from the Tanaka equation (208 − 0.7 × age), validated as more accurate across ages than the folk-standard 220 − age. The Karvonen method then applies your chosen intensity fraction to heart-rate *reserve*; the span between max and resting; and re-adds resting rate.

Because reserve-based zones account for fitness (lower resting HR widens the reserve), they personalize better than raw percentages of maximum alone.

Assumptions & limitations

  • Morning resting HR measured reliably.
  • Tanaka HRmax carries ±10 bpm individual error; zones shift with it.
  • Not medical guidance; cardiac patients need clinically determined limits.

Worked example

At age 30 with a resting rate of 60 bpm, HRmax estimates to 187 bpm and 70%-reserve training lands near 149 bpm, inside the steady-tempo zone.

FAQ

Frequently asked questions

My wearable says my HRmax differs; who wins?
Your measured max from a truly all-out effort beats any equation. Enter it implicitly via zones once known; until then trust Tanaka over 220 − age.
Do medications affect this?
Beta-blockers suppress both resting and maximum heart rate substantially; cardiac patients must use clinician-prescribed ranges, not formulas.
Why did the calculator refuse my resting HR?
Resting rate must sit below the estimated maximum to define a positive reserve; otherwise the inputs contradict each other physiologically.

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