How to Find Your Zone 2 Heart Rate: Karvonen Formula & Fat Oxidation

Zone 2 training has become the cornerstone of endurance athletics and longevity medicine. In Zone 2, your body relies primarily on Type I slow-twitch muscle fibers and fat oxidation, stimulating mitochondrial biogenesis, lactate clearance, and cardiovascular stroke volume.

This guide explains how to calculate your 5 training zones using the Tanaka and Karvonen Heart Rate Reserve (HRR) formulas, and links to the CalculatorAll Heart Rate Zone Calculator.

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The Tanaka & Karvonen Formulas

1. Estimate Max Heart Rate (Tanaka Formula)

Max HR (HRmax) = 208 - (0.7 × Age)

(Note: The Tanaka equation is clinically superior to the legacy 220 - Age formula for active adults).

2. Calculate Heart Rate Reserve (HRR)

Heart Rate Reserve (HRR) = HRmax - Resting Heart Rate (HRrest)

3. Calculate Zone 2 Target Range (60% to 70% of HRR)

Zone 2 Low (BPM) = (HRR × 0.60) + HRrest Zone 2 High (BPM) = (HRR × 0.70) + HRrest

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Worked Example: 35-Year-Old with 60 BPM Resting Pulse

1. Calculate Max HR: 208 - (0.7 × 35) = 208 - 24.5 = 183.5 BPM.
2. Calculate HRR: 183.5 - 60 = 123.5 BPM.
3. Calculate Zone 2 Low (60%): (123.5 × 0.60) + 60 = 74.1 + 60 = 134 BPM.
4. Calculate Zone 2 High (70%): (123.5 × 0.70) + 60 = 86.45 + 60 = 146 BPM.
5. Zone 2 Target: 134 to 146 BPM.

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The "Talk Test" for Zone 2 Validation

If you do not wear a chest strap heart rate monitor, use the Talk Test: in Zone 2, you should be able to speak full, unbroken conversational sentences without gasping for breath, while breathing primarily through your nose. If you can only speak in 3-word bursts, you have crossed into Zone 3/4.