How Zone 2 Heart Rate Calculator works

Scope

Estimates the Zone 2 aerobic training range using four independent definitions: Maffetone 180-age, Karvonen at 60–70% HRR, a straight 60–70% of max HR, and a lactate-threshold-anchored range.

Zone 2 is the intensity where mitochondrial adaptation and fat oxidation dominate. The definitions differ enough that the right choice depends on your training history.

Formula

Maffetone: ceiling = 180 - age (+/- adjustments). Karvonen Z2: (MHR - RHR) * [0.60, 0.70] + RHR. %MHR Z2: MHR * [0.60, 0.70]. LT-anchored Z2: [0.80, 0.88] * LTHR.

Coefficients

Data sources

1. Maffetone P. The Maffetone Method. Ragged Mountain Press, 1999. — Author reference page documenting the 180-age formula and its adjustment rules.
2. Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn. 1957;35(3):307-315. — PMID 13470504. Origin of the heart-rate reserve formula.
3. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010;5(3):276-291. — PMID 20861519. Background on the polarized/pyramidal model and the role of Z2.
4. San-Millán I, Brooks GA. Assessment of metabolic flexibility by means of measuring blood lactate, fat, and carbohydrate oxidation responses to exercise in professional endurance athletes and less-fit individuals. Sports Med. 2018;48(2):467-479. — PMID 28623613. Metabolic rationale for training at the Zone 2/LT1 intensity.

Assumptions

• If a lactate threshold HR (LTHR) is known from a 30-minute time-trial field test, use the LT-anchored range — it is the most individually calibrated.
• Resting HR is a true resting reading, not a post-coffee reading.

Approximation range

Maffetone tends to prescribe the most conservative ceiling, especially for lifters and short-course athletes moving into endurance.

Karvonen-HRR tends to fall 5–10 bpm above the Maffetone ceiling for the same athlete.

All four definitions agree within ~12 bpm for typical adults; the spread is the point of displaying them together.

Limitations

• No HR-based zone definition can distinguish between fat-oxidation-dominant and carbohydrate-dominant work at the same HR; metabolic cart or lactate testing is the ground truth.
• HR drift on long runs inflates numbers by 5–15 bpm vs minute-1 of the same effort; Z2 prescriptions should be taken as 'HR at minute-20 steady state'.
• Stimulants, dehydration, and heat materially shift zones.

Reproducibility

35 yo, MHR 185, RHR 55, LTHR 162. Maffetone ceiling 180-35 = 145. Karvonen Z2 (0.60–0.70): (185-55)*0.60+55 = 133; (185-55)*0.70+55 = 146. %MHR Z2: 111–130. LT-anchored Z2: 0.80*162 = 130; 0.88*162 = 143.

Change log

• 2026-04-24: methodology page first published.

Related tools

• Running Pace Calculator — Calculate pace per km and mile and project race finish times from one run.
• VO2 Max Estimator — Estimate aerobic capacity with the Cooper 12-minute run or Rockport 1-mile walk field tests.
• Walking Calorie Calculator — Estimate calories burned from walking using speed, duration, body weight, and incline.
• Calories Burned Calculator — Estimate exercise calorie burn from body weight, duration, MET intensity, and incline.

Worked example

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FAQ

What is Zone 2 heart rate training and why does it matter?

Zone 2 is the aerobic intensity corresponding to the first ventilatory threshold, where your body primarily oxidizes fat as fuel and builds mitochondrial density in slow-twitch muscle fibers. Research by San Millan and Brooks (2018) at the University of Colorado identified this zone as the intensity that maximally stimulates mitochondrial biogenesis, which improves metabolic health, insulin sensitivity, and cardiovascular function. Dr. Peter Attia has called Zone 2 training 'the single most important exercise modality for longevity.' The recommended dose is 3-4 sessions of 45-60 minutes per week, totaling 150-240 minutes. At this intensity, you should be able to speak in full sentences without pausing for breath.

Which Zone 2 calculation method is most accurate?

No formula is perfectly accurate without laboratory lactate testing or a ventilatory threshold test. The Karvonen method (heart rate reserve) is the most individualized because it accounts for both max HR and resting HR, adjusting the zone for your cardiovascular fitness level. If you only know your age, the Maffetone MAF 180 formula (180 - age, with adjustments for training status and health conditions) is a reliable conservative starting point developed by Dr. Phil Maffetone and used by endurance coaches worldwide since the 1980s. The percentage-of-max-HR method (60-70%) is the simplest but least personalized. For serious athletes, a laboratory lactate threshold test at 2 mmol/L defines Zone 2 precisely.

Why do the four methods give different Zone 2 ranges?

Each method uses different physiological assumptions and inputs. The Maffetone MAF 180 formula uses only age and produces a single ceiling number, making it conservative. The percentage-of-max-HR method applies 60-70% to an estimated max HR (220-age or Tanaka formula) but ignores resting HR entirely. The Karvonen method accounts for heart rate reserve (max HR minus resting HR), producing a range that adjusts for fitness level. The lactate-threshold-derived estimate uses a fraction of estimated max HR to approximate where blood lactate begins accumulating. A wider spread between methods in your results indicates greater input uncertainty, and providing your actual resting HR and tested max HR narrows the gap significantly.

Should I use the 220-minus-age formula or the Tanaka formula for max heart rate?

The Tanaka formula (208 - 0.7 x age), published by Tanaka, Monahan, and Seals in 2001 in the Journal of the American College of Cardiology, is more accurate than 220-age, particularly for adults over 40. The traditional 220-age formula was never derived from original research but was an approximation that appeared in published guidelines without rigorous validation. For a 50-year-old, 220-age predicts max HR of 170 bpm while Tanaka predicts 173 bpm. The difference grows with age: at 60, 220-age gives 160 while Tanaka gives 166 bpm. Neither formula replaces an actual graded exercise test, which is the gold standard and can reveal individual max HR values that deviate by 10-20 bpm from any formula.

How do I verify that I am actually training in Zone 2?

Three practical validation methods exist. The talk test: you should be able to speak in full, continuous sentences without needing to pause for breath. If you can only manage short phrases, you are above Zone 2. Nasal breathing: if you can sustain breathing exclusively through your nose during exercise (mouth closed), you are likely at or below Zone 2. If you must open your mouth to breathe, you have crossed the threshold. Heart rate monitor: a chest strap or optical sensor confirms you are within your calculated Zone 2 range. For definitive validation, a single lactate test at a sports medicine clinic establishes your personal lactate threshold at 2 mmol/L, which precisely defines the top of your Zone 2.

How much Zone 2 training should I do per week?

The evidence-based recommendation supported by research from Seiler and Kjerland (2006) and the current practice of elite endurance athletes is 3-4 sessions of 45-60 minutes each, totaling approximately 150-240 minutes per week. Elite endurance athletes spend roughly 80% of their total training volume at Zone 2 intensity, with only 20% at higher intensities. For non-athletes focused on health and longevity, 150 minutes per week is the minimum effective dose described in WHO physical activity guidelines. Activities that work well for Zone 2 include walking briskly, cycling at a conversational pace, swimming, rowing, and elliptical training.