How this instrument works
Anaerobic threshold is the effort level where your muscles start producing lactate faster than your body can clear it. Below that point, you're working aerobically and could sustain the pace for a long time; push past it and fatigue builds quickly because the byproducts of anaerobic metabolism start accumulating. Exercise physiologists commonly place this transition at roughly 85% of maximum heart rate for most trained adults, with a practical training band running from about 80% to 90% — this calculator returns the midpoint estimate plus that low-high range.
Since anaerobic threshold is a percentage of max heart rate (HRmax), the accuracy of the estimate depends entirely on the HRmax formula behind it. This calculator offers three: the classic Fox & Haskell 220-minus-age formula from 1971, the Nes/HUNT-study formula (211 − 0.64 × age) derived from a large Norwegian population study, and Tanaka, Monahan & Seals' 208 − 0.7 × age formula, a 2001 meta-analysis of 351 studies that's now widely considered the more accurate modern alternative, especially for older adults where 220-age tends to underestimate true HRmax.
None of these formulas measure your actual physiology — they're population regressions with real individual scatter (a standard deviation of roughly 7-11 beats per minute is typical), so treat the output as a solid starting estimate for structuring interval or tempo training, not a lab-verified number. A real anaerobic threshold test (blood lactate sampling or ventilatory gas analysis during a graded exercise test) is the only way to pin down your true value.
- Enter your Age in years.
- Pick a Max heart-rate formula — Tanaka/Monahan/Seals is the modern default, Fox & Haskell is the traditional 220-age formula, and Nes/HUNT is a third population-based alternative.
- Read Estimated maximum heart rate — the HRmax the rest of the calculation is built from.
- Read Anaerobic threshold (85% HRmax) — your central estimate, plus the 80% and 90% boundary values that frame the usual training band.
- Use the low-high range to set interval or tempo-run target zones rather than chasing one exact number.
Worked example — a 30-year-old using the Tanaka formula
Enter 30 for age and select the Tanaka, Monahan & Seals formula. HRmax comes out to 208 − 0.7 × 30 = 187 bpm. The anaerobic threshold estimate is then 187 × 0.85 = 158.95 bpm, with a training band running from 187 × 0.80 = 149.6 bpm up to 187 × 0.90 = 168.3 bpm.
That roughly 150-168 bpm range is where a lot of tempo and threshold-interval work gets prescribed for this athlete — comfortably hard, sustainable for 20-60 minutes depending on fitness, but not an all-out sprint effort. A heart-rate monitor showing readings consistently above 168 bpm during a 'threshold' session signals the pace is really landing closer to VO2max effort instead.
Questions
What exactly happens at anaerobic threshold?
Below anaerobic threshold, your muscles produce lactate at a rate your body can clear just as fast, so blood lactate stays fairly stable even as you keep exercising. Push past that intensity and lactate production outpaces clearance, so it starts accumulating in the blood — you'll feel breathing get noticeably harder and the pace becomes unsustainable within minutes rather than hours. It's also sometimes called the lactate threshold or, more precisely, the onset of blood lactate accumulation (OBLA).
Why does this calculator offer three different max-heart-rate formulas?
All three are legitimate, widely cited population regressions, but they were built from different samples and give meaningfully different answers, especially past age 40. Fox & Haskell's 220-age (1971) is the oldest and most familiar but tends to overestimate HRmax in younger people and underestimate it in older adults. Tanaka, Monahan & Seals (2001) pooled data from 351 studies and is now the more commonly recommended default; Nes/HUNT is a third large-population alternative. None is 'correct' for every individual — picking one consistently and tracking trends matters more than which formula you choose.
Is 85% of HRmax always my true anaerobic threshold?
No — 85% is a widely used population-average estimate, not a personal measurement. Untrained individuals often sit closer to 70-75% of HRmax, while highly trained endurance athletes can push anaerobic threshold up toward 90% or more of HRmax. The 80-90% range this calculator returns reflects that real spread; a formal lactate or ventilatory threshold test is the only way to find your specific number.
How is anaerobic threshold different from VO2max?
VO2max is the absolute ceiling on how much oxygen your body can use during maximal effort — a single peak number. Anaerobic threshold is the intensity, well below that ceiling, where your metabolism shifts from mostly aerobic to increasingly anaerobic. Training can raise anaerobic threshold closer to VO2max even without changing VO2max itself, which is exactly what a lot of tempo and threshold training is designed to do — it lets you sustain a faster pace before the 'anaerobic' fatigue kicks in.
How should I use my anaerobic threshold number in training?
Threshold-pace work — intervals or a sustained tempo effort held right around your estimated anaerobic-threshold heart rate — is a standard way to raise the pace you can hold before lactate starts piling up. Training just below threshold builds aerobic durability; training at or slightly above it (with recovery) improves your body's ability to buffer and clear lactate. Because the formula-based estimate carries real error, most coaches recommend adjusting the target zone based on how a session actually feels (perceived effort, breathing rate) rather than chasing the number exactly.