Two Ways to Set Zones — and Why They Disagree
The Karvonen method computes zones from your heart-rate reserve — the gap between your max and your resting rate. Because a lower resting heart rate generally reflects better fitness, Karvonen shifts a fit person's zones upward: your easy zone is a higher number than a beginner's easy zone, which is exactly right.
The % of max HR method ignores resting rate entirely: each zone is just a percentage of your estimated max (220 minus age, in both methods here). It's simpler, it's what most watches and gym machines default to, and it systematically produces lower zone numbers than Karvonen for the same person. Neither is "wrong" — just don't compare your Karvonen Zone 2 to a friend's watch Zone 2 and conclude one of you is fitter.
Zone 2: The One Everyone Keeps Talking About
Zone 2 — roughly 60–70% of reserve, the pace where you can still hold a full conversation — is where the endurance world has landed after decades of trial data. It builds mitochondrial density and aerobic efficiency with remarkably little fatigue or injury risk, which is why elite endurance athletes spend most of their training time here (the famous "80/20" polarized split: 80% easy, 20% genuinely hard, with little in between).
The practical version for regular people: 2–3 sessions of 30–60 minutes in Zone 2 per week does most of what training plans promise — and the most common mistake is running Zone 2 runs too fast, drifting into the no-man's-land of Zone 3, which is hard enough to accumulate fatigue but easy enough to build little speed.
The Talk Test: Zones Without Any Math
Before heart rate monitors, coaches used speech as the gauge, and it holds up well against lab measurements: full sentences = Zone 2, short phrases = Zone 3, single words = Zone 4, nothing = Zone 5. If your watch says Zone 2 but you can't speak a full sentence, believe your breathing — chest straps and wrist sensors misread more often than lungs do.
Common Questions
How do I find my resting heart rate?
Measure it first thing in the morning before getting out of bed: count your pulse for 60 seconds (or 30 seconds × 2), and repeat for three mornings, then average. Most adults land between 60 and 100 bpm; regular exercisers often sit in the 50s or 40s. A sudden rise of 5–10 bpm over your normal can signal illness, overtraining, or poor recovery.
Why are my watch's zones different from this calculator?
Two common reasons. Method: most watches default to simple % of max HR, which produces lower numbers than the Karvonen method this calculator defaults to — switch the toggle above to '% of max HR' to match. Calibration: watches estimate max HR from your age (220 − age has a ±12 bpm standard error) and adjust it from workout data; if your watch has learned your true max, trust it over any formula.
What is Zone 2 and why does everyone recommend it?
Zone 2 is roughly 60–70% of your heart-rate reserve — an easy, conversational pace where you can speak in full sentences. It builds aerobic base, mitochondrial density, and fat metabolism with minimal fatigue or injury risk, which is why elite endurance athletes spend about 80% of training time there. For most people, 2–3 sessions of 30–60 minutes a week in Zone 2 delivers most of cardio's health benefits.
Is the 220 minus age formula accurate?
It's an estimate with a standard error of about 12 bpm — fine for setting training zones, crude for individuals. The Tanaka formula (208 − 0.7 × age) fits older adults better, and a lab or field test (like a hard ramp effort with supervision) is the real gold standard. If you've ever seen your heart rate above your estimated max during all-out effort, your true max is higher than the formula says.
Related Calculators
- Calorie Calculator — Daily calorie needs (TDEE)
- Calories Burned Calculator — Burn by activity and duration
- BMR Calculator — Your baseline metabolism