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Free Training Tool

Zone 2 Heart Rate Calculator

Find your personalised training zones using the Karvonen (heart rate reserve) formula, the method used by elite endurance coaches worldwide.

Karvonen formula All 5 training zones Free, no sign-up

Enter Your Details

Your resting heart rate makes this calculation personal to you, don't skip it.

Between 10 and 100

Measure on waking. Typical range: 40–80 bpm.

How to Use This Calculator

  1. Measure your resting heart rate

    First thing in the morning, before getting out of bed, count your pulse for 60 seconds. Repeat for 3 consecutive mornings and average the results. A smartwatch worn overnight can automate this.

  2. Enter your age and resting HR

    Age is used to estimate maximum heart rate (HRmax = 220 − age). Resting HR personalises the calculation via heart rate reserve (HRR = HRmax − RHR), making zones specific to your fitness level.

  3. Read your Zone 2 range

    Your Zone 2 target is highlighted in the results. Most people are surprised how slow they need to go to stay in Zone 2, this is normal and is why the zone is often called "conversational pace."

  4. Train consistently in Zone 2

    Aim for 3–4 sessions per week of 45–90 minutes each. Running, cycling, rowing, and brisk walking all work well. Benefits compound over months: improved fat oxidation, lower resting HR, and greater aerobic efficiency.

The Karvonen Formula Explained

Karvonen Formula

HRmax = 220 − Age

HRR = HRmax − Resting HR

Target HR = Resting HR + (HRR × Intensity %)

Zone 2 uses 60–70% of HRR

The Karvonen formula (1957) is the gold standard for calculating personalised heart rate training zones because it accounts for your cardiovascular fitness through resting heart rate. A trained athlete with a resting HR of 45 bpm will get different (and lower) zone targets than a sedentary person with the same age and a resting HR of 75 bpm, as it should be.

Why Zone 2 matters: research by Stephen Seiler and others on elite endurance athletes consistently found that ~80% of their training volume sits at low intensity (Zones 1–2), with only ~20% at high intensity. This polarised distribution produces superior aerobic adaptations compared to moderate-intensity training alone. At Zone 2, the primary fuel source is fat, and the primary training stimulus is mitochondrial biogenesis, increasing the number and efficiency of mitochondria in slow-twitch muscle fibres.

Limitations: The 220 − age formula has a standard deviation of ±10–12 bpm, meaning your true max HR could differ significantly from the estimate. The Tanaka formula (208 − 0.7 × age) is more accurate for adults over 40. For precise zone boundaries, a lactate threshold test or supervised VO₂ max test is recommended. The talk test is a practical real-world validator: at the top of Zone 2, you should still be able to speak in short sentences.

Zone Name HRR % Primary Benefit
1 Active Recovery 50–60% Blood flow, recovery
2 Aerobic Base★ 60–70% Fat oxidation, mitochondria
3 Aerobic Tempo 70–80% General aerobic fitness
4 Threshold 80–90% Lactate threshold
5 VO₂ Max 90–100% Maximal aerobic power

Frequently Asked Questions

What is Zone 2 heart rate training?
Zone 2 is the aerobic base zone, 60–70% of your heart rate reserve. It is the intensity at which your body primarily burns fat for fuel and produces the strongest stimulus for mitochondrial biogenesis. You should be able to hold a broken conversation at this effort level. It is the single most studied and endorsed training zone for cardiovascular longevity and athletic base building.
How long should Zone 2 sessions be?
For meaningful adaptation, target 45–90 minutes per session, 3–4 times per week. Research on elite endurance athletes suggests Zone 2 should make up roughly 80% of total weekly training volume. Beginners can start with 30-minute sessions and build from there.
How accurate is the Karvonen formula?
More accurate than simple % of max HR because it personalises to your resting HR. However, the HRmax estimate (220 − age) has a ±10–12 bpm standard deviation. For greater precision, use a lab-measured HRmax or consider the Tanaka formula (208 − 0.7 × age) for adults over 40.
What is the best equipment for Zone 2 training?
A chest-strap heart rate monitor provides ECG-quality accuracy and is the most reliable option during running, where wrist-based optical sensors can be off by 5–20 bpm due to wrist movement. Any aerobic activity, running, cycling, rowing, swimming, brisk walking, can be performed in Zone 2.
Why does Zone 2 feel so slow?
For most people who habitually train at moderate intensity (Zone 3), Zone 2 feels uncomfortably easy, you have to actively slow down to stay in range. This is because years of moderate-intensity training can limit aerobic development. As your aerobic base builds over months, you will be able to move faster at the same heart rate.

Track Zone 2 Accurately with a Chest Strap

Wrist-based optical sensors can read 5–20 bpm too high during running due to wrist movement, enough to push you into Zone 3 without knowing. A chest-strap heart rate monitor provides ECG-quality accuracy (±1 bpm) and pairs with any GPS watch, cycling computer, or treadmill.

Affiliate disclosure: we earn a small commission on qualifying purchases at no extra cost to you. Our recommendations reflect performance and value, not commission rate.

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