MAF heart
rate

Your maximum aerobic heart rate from the Maffetone 180 formula — subtract your age from 180, then one health-and-training adjustment. Enter both and get the aerobic ceiling, the training window below it, and where that number lands on the percent-of-max zones.

How the math works

The 180 formula sets a single ceiling for aerobic training. Start at 180, subtract your age, then apply one adjustment for health and training status. The result is the top of your aerobic range; the method is to train in the 10-bpm window below it, not at it.

Two special cases sit outside the formula. For anyone 16 and under, the age subtraction doesn't apply and a fixed 165 bpm is used instead. For an athlete over 65 who is genuinely in category (d), up to 10 bpm may be added — on an honest self-assessment, not automatically.

The MAF test is how you check whether it's working: hold the MAF heart rate over a fixed distance and repeat it every few weeks. When the same heart rate buys a faster pace, aerobic fitness has risen. That field measurement, not the formula, is the number that matters over time.

Worked example

A 40-year-old runner in category (c) — training at least four times a week for under two years, no injuries or health flags. The formula gives 180 − 40 = 140 bpm as the aerobic ceiling, so the training window is 130–140 bpm. Change only the category and the ceiling shifts: (a) 130, (b) 135, (c) 140, (d) 145 bpm.

Here is the part most MAF calculators leave out. Put that same 140 bpm on the percent-of-max zones. Tanaka's max-HR estimate for a 40-year-old is 208 − 0.7 × 40 = 180 bpm, so 140 bpm is 78% of max (140 ÷ 180) — which is Zone 3, "tempo", on the ACSM five-zone model. The whole MAF window, 130–140 bpm, sits in Zone 3:

The percent-of-max model calls its aerobic zone Zone 2, and Zone 2 tops out at 126 bpm for this runner — about 14 bpm below the MAF ceiling. So the two popular methods draw the "easy aerobic" line roughly a full zone apart. Heart rate is beats per minute, the same number everywhere; there is no imperial-versus-metric version of it. Units only re-enter when you pair the ceiling with pace — an easy effort might sit near 9:30–10:00/mi (5:54–6:13/km) for a mid-pack runner (Scenario E2), and that pace has two unit forms while the heart rate has one.

When this calculator is wrong

The MAF number and the percent-of-max zones disagree about where easy aerobic ends, and neither is a measured threshold. For the 40-year-old above, the 180 formula caps aerobic work at 140 bpm, but that's 78% of Tanaka's estimated max — the top of Zone 3, whose aerobic Zone 2 ends at 126 bpm. The two methods sit about 14 bpm — roughly a full zone — apart, purely because one subtracts age from a fixed 180 and the other takes a percentage of an age-estimated maximum. The 180 formula in particular has no published error band against a lab-measured aerobic threshold.

The exception is the failure mode the MAF cap is built to fix: runners who let easy days drift too hard. A single ceiling you actually hold to beats a more "accurate" band you round up out of. Polarised-training research (Seiler 2010: roughly 80% of endurance work easy, 20% hard) says most of your volume should be easy whichever model drew the line, and a hard cap enforces that even when it's approximate. The right calibration isn't picking between two formulas — it's the MAF test: pace improving at the same heart rate.

• Medication and heart conditions break it. Beta-blockers and other rate-lowering drugs decouple heart rate from effort, so a heart-rate ceiling stops describing intensity. That's a clinician question, not a mechanical −10.
• The category is a self-report. The adjustment swings the ceiling by up to 15 bpm across (a) to (d). Honest placement matters more than the arithmetic — most people are closer to (b) or (c) than to (d).
• Very fit or very new athletes are edge cases. A highly trained runner may find the cap frustratingly low at first; a beginner may not be able to hold a steady effort there at all. Give it several weeks before judging it.

What to do with the result

Treat the ceiling as a hard cap on easy and base-building sessions, and run most of them in the 10-bpm window below it. Confirm it with a talk test: if you can't speak in full sentences, you've drifted above the cap regardless of what the watch says. Then run the MAF test every three or four weeks — hold the ceiling over a fixed distance and track the pace. Rising pace at the same heart rate is the signal the base is building; flat or falling pace over months is the signal to check recovery, category placement, or non-training stress. Recompute when your training status changes a category, or on a birthday that shifts the number by a beat.

Common questions

How do I calculate my MAF heart rate?

Subtract your age from 180, then apply one adjustment: −10 if you're recovering or on regular medication, −5 if you're injured, inconsistent, or get frequent colds, 0 if you've trained consistently for up to two years without issues, or +5 if you've trained more than two years, are progressing, and are injury-free. A 40-year-old in the "consistent, no issues" category gets 180 − 40 = 140 bpm, and trains in the 130–140 bpm window below it.

Is the MAF heart rate the same as Zone 2?

Not exactly. On the percent-of-max model, a 40-year-old's MAF ceiling of 140 bpm is about 78% of estimated max heart rate — that's Zone 3 (tempo), not Zone 2, whose aerobic band ends around 126 bpm for the same runner. The two methods define "easy aerobic" differently and land about a full zone apart. MAF is its own aerobic ceiling, not a relabelled Zone 2.

Why subtract age from 180 specifically?

180 is the fixed anchor Phil Maffetone chose for the formula; the adjustments then personalise it for health and training history. It isn't derived from a measured maximum heart rate, which is why the number can differ from your percent-of-max zones. It's a practical heuristic for capping aerobic effort, validated in practice rather than against lab thresholds.

Should I train at the MAF heart rate or below it?

Below it. The MAF number is a ceiling, and the method is to train in the 10-bpm window under it for easy and base-building work. Touching the ceiling occasionally is fine; sitting above it defeats the purpose, which is keeping aerobic sessions genuinely aerobic.

How long until MAF training improves my pace?

Weeks to months, tracked by the MAF test — holding the ceiling over a fixed distance and watching the pace. When the same heart rate buys a faster pace, the aerobic base is building. If the pace stays flat over a couple of months, look at recovery, non-training stress, or whether your category placement is honest, rather than raising the cap.

Does the formula work if I'm on beta-blockers?

No. Beta-blockers and similar medications lower both resting and maximum heart rate and decouple heart rate from effort, so a heart-rate ceiling no longer describes intensity. Use perceived effort or a talk test instead, and ask the prescribing clinician how to gauge training intensity while on the medication.