MAF Heart Rate Calculator
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How the formula works
Phil Maffetone's "180-formula" approximates the upper end of Zone 2 (aerobic base) intensity without requiring lab testing. Start with 180, subtract your age, then adjust based on training history. The result is the ceiling — train mostly 10 bpm below that.
How to use it
- For 80% of weekly cardio time, stay below your MAF number.
- Use nose-only breathing as a corroboration cue — if you can't breathe nasally, you're likely above Zone 2.
- Re-test monthly: same effort should produce same HR. If HR drops at the same pace, aerobic base is improving.
FAQ
Is MAF the same as lactate threshold Zone 2?
Approximately. MAF is a simple proxy. Lab-measured Zone 2 (where blood lactate is < 2 mmol/L) can differ slightly. Both are within the aerobic base intensity range.
Can I exceed MAF in workouts?
Yes. The 80/20 rule says 80% of training time below MAF, 20% can be harder. The mistake is doing 100% in the gray zone above MAF but below threshold — that produces fatigue without aerobic gains.