Zone 2 Heart Rate: How to Calculate Your Exact Training Zone

You have heard that Zone 2 cardio is the foundation of a longevity-focused training program. The problem is figuring out what Zone 2 actually means for your body. A 135 bpm heart rate might be Zone 2 for one person and Zone 3 for another.

Here are four methods to calculate your Zone 2, ranked from least to most accurate.

Method 1: The Age-Based Formula (Least Accurate)

The classic formula estimates your max heart rate as 220 minus your age, then sets Zone 2 at 60-70% of that number.

Example for a 35-year-old:

• Estimated max HR: 220 - 35 = 185 bpm
• Zone 2 range: 111 - 130 bpm

This method is free and instant. It is also wrong for a large percentage of people. The 220-minus-age formula has a standard deviation of about 10-12 bpm, meaning your actual max heart rate could easily be 10-15 beats higher or lower than predicted.

Method 2: The Karvonen Formula (Better)

The Karvonen method accounts for your resting heart rate, which makes it more individualized. It uses heart rate reserve (HRR) -- the difference between your max and resting heart rate.

Formula: Target HR = ((Max HR - Resting HR) x % Intensity) + Resting HR

Example for a 35-year-old with a resting HR of 58:

• Max HR estimate: 185 bpm
• Heart rate reserve: 185 - 58 = 127 bpm
• Zone 2 lower: (127 x 0.60) + 58 = 134 bpm
• Zone 2 upper: (127 x 0.70) + 58 = 147 bpm

This is meaningfully better than the simple percentage method because it accounts for your baseline fitness. A well-trained athlete with a resting heart rate of 48 will get a different range than a sedentary person at 72 bpm.

Getting an Accurate Resting Heart Rate

Measure your resting heart rate first thing in the morning, before getting out of bed, for at least 5 consecutive days. Take the average. Wearables like Oura Ring or WHOOP track this automatically and provide a more reliable average than a single measurement.

Method 3: The MAF Method (Simple and Practical)

Dr. Phil Maffetone's MAF (Maximum Aerobic Function) formula is popular in the endurance community: subtract your age from 180, then adjust.

Base formula: 180 - age = MAF heart rate

Adjustments:

• Subtract 10 if recovering from illness or on medication
• Subtract 5 if you have not been training consistently
• Add 0 if you have been training consistently for 2+ years
• Add 5 if you are an elite athlete who has been training for 5+ years

Example for a consistently training 35-year-old:

• MAF HR: 180 - 35 = 145 bpm
• Zone 2 range: 135 - 145 bpm

The MAF method tends to produce slightly higher numbers than the standard formula, which many practitioners find more practically useful. Train at or below your MAF number.

Method 4: Lactate Testing (Gold Standard)

The most accurate way to determine Zone 2 is a graded exercise test with blood lactate measurements. This is the method used by exercise physiologists and elite sports programs.

During the test, you exercise at progressively increasing intensities while a technician measures blood lactate at each stage. Your Zone 2 upper boundary is the intensity at which lactate begins to accumulate above baseline -- typically around 2 mmol/L.

This test costs $150-300 at most sports performance labs and provides personalized, precise heart rate zones that no formula can match.

Validating Your Zone Without a Lab

If a lactate test is not practical, you can cross-reference your calculated zone with these real-world checks:

• Talk test: You should be able to speak in complete sentences. If you can only get out a few words between breaths, you are above Zone 2.
• Nasal breathing: Most people can breathe exclusively through their nose during true Zone 2 work. If you need to mouth-breathe, drop the intensity.
• Rate of perceived exertion: Zone 2 should feel like a 3-4 out of 10. Comfortable but not effortless. You could sustain it for hours.
• Cardiac drift: In a properly-paced Zone 2 session, your heart rate should remain relatively stable. If it climbs steadily throughout the session despite constant effort, you started too high.

Putting It Together

Start with the Karvonen or MAF method, validate with the talk test and nasal breathing, and get a lactate test when it makes sense for your budget and goals.

This article is for informational purposes only and does not constitute medical advice. Consult a healthcare provider before starting a new exercise program.