Heart Rate Zone Calculator
What heart rate should an easy run be — and what counts as Zone 2? Enter your age to get all five training zones in bpm, and add your resting heart rate to switch to the more personalized Karvonen method.
measure on waking
Max HR — Tanaka (used below)
180 bpm
208 − 0.7 × age · better validated
Max HR — classic
180 bpm
220 − age
Z1 Recovery — very easy (50–60%)
90–108 bpm
Z2 Endurance / fat-burn (60–70%)
108–126 bpm
Z3 Aerobic — moderate (70–80%)
126–144 bpm
Z4 Threshold — hard (80–90%)
144–162 bpm
Z5 Maximum effort (90–100%)
162–180 bpm
Both max-HR formulas carry roughly ±10 bpm of individual spread — a field test or lab test is the only way to know yours exactly. Without a resting HR, zones are plain percentages of max; adding one switches to Karvonen, which shifts every zone higher. General fitness guidance only — not medical advice.
Plain Percentages vs. Karvonen
The same “70%” means two very different heart rates depending on the method. For a 40-year-old (max HR 180 by both 220 − age and Tanaka's 208 − 0.7 × age), a plain 70% of max is 126 bpm. The Karvonen method instead takes 70% of the heart-rate reserve— with a resting HR of 60, that's (180 − 60) × 0.7 + 60 = 144 bpm. Karvonen runs higher because it accounts for the fact that your heart never drops to zero; it's the better anchor once you know your true resting rate.
The five zones (age 40, max HR 180)
Zone %max plain bpm Karvonen (RHR 60) Z1 50–60% 90–108 120–132 recovery Z2 60–70% 108–126 132–144 endurance/fat-burn Z3 70–80% 126–144 144–156 aerobic Z4 80–90% 144–162 156–168 threshold Z5 90–100% 162–180 168–180 max effort Karvonen: zone bpm = (maxHR − restHR) × % + restHR
Frequently Asked Questions
What heart rate burns the most fat?
Zone 2 — about 60–70% of max heart rate — burns the highest proportion of calories from fat, which is why it's called the fat-burn zone. For a 40-year-old that's roughly 108–126 bpm (or 132–144 bpm by Karvonen with a resting HR of 60). Higher zones burn a smaller fat fraction but more total calories per minute, so for weight loss the best zone is largely the one you can sustain longest.
Is the 220 minus age formula accurate?
It's a rough population average with roughly ±10 bpm of individual spread, and it systematically underestimates max HR in older adults. The Tanaka formula (208 − 0.7 × age), built from a meta-analysis of over 18,000 subjects, is better validated — this calculator uses it for the zone math. At age 40 both formulas happen to give 180 bpm; they diverge as you get older.
What is the Karvonen formula for heart rate?
Karvonen anchors zones to your heart-rate reserve instead of a flat percentage of max: zone bpm = (max HR − resting HR) × intensity % + resting HR. For a 40-year-old with a max of 180 and a resting HR of 60, 70% intensity is (180 − 60) × 0.7 + 60 = 144 bpm — versus 126 bpm as a plain 70% of max. It personalizes zones because a fitter heart has a lower resting rate and therefore a bigger reserve.
What heart rate zone should most of my running be in?
Endurance coaching broadly follows an 80/20 split: about 80% of weekly volume in Zones 1–2 (easy, conversational pace) and 20% in Zones 4–5 (threshold and interval work). Zone 3 is the famous 'gray zone' — hard enough to fatigue you, not hard enough to drive top-end adaptations — so most structured plans deliberately minimize it.