What Is Zone 2?
Zone 2 is the second of five heart rate training zones, sitting at 60–70% of your maximum heart rate. At this intensity you're working steadily — sweating, breathing noticeably — but you can still hold a full conversation without pausing to catch your breath. It's not a warm-up and it's not a workout that leaves you gasping. It's a sustained, aerobic effort you could maintain for hours.
This zone has become one of the most talked-about concepts in endurance and longevity training because the adaptations it produces — more mitochondria, better fat metabolism, a stronger heart — compound over months without the recovery cost that harder zones demand. You can do a lot of it.
How to Calculate Your Zone 2 Heart Rate
Start with your estimated maximum heart rate. The most widely used formula is:
From there, multiply by 0.60 and 0.70 to get the lower and upper bounds of your Zone 2 range:
Example — age 35: Max HR = 220 − 35 = 185 bpm. Zone 2 = 0.60 × 185 to 0.70 × 185 = 111–130 bpm. That's the range to stay in during a Zone 2 run, ride, or rowing session.
The Karvonen Method (More Accurate)
The simple formula treats all 35-year-olds the same, regardless of fitness. The Karvonen method corrects for that by factoring in your resting heart rate — a direct measure of cardiovascular fitness. It uses your heart rate reserve: the range between resting and max.
Example — age 35, resting HR 58 bpm: Heart rate reserve = 185 − 58 = 127. Zone 2 = 58 + (76 to 89) = 134–147 bpm. That's significantly higher than the simple formula gives — and for a trained person with a low resting HR, it's far more accurate.
Zone 2 Range by Age
The table below uses the 220 − age formula. If you know your resting heart rate, use the Karvonen method or the calculator above for a more precise number.
| Age | Est. Max HR | Zone 2 Lower (60%) | Zone 2 Upper (70%) |
|---|---|---|---|
| 20 | 200 bpm | 120 bpm | 140 bpm |
| 25 | 195 bpm | 117 bpm | 137 bpm |
| 30 | 190 bpm | 114 bpm | 133 bpm |
| 35 | 185 bpm | 111 bpm | 130 bpm |
| 40 | 180 bpm | 108 bpm | 126 bpm |
| 45 | 175 bpm | 105 bpm | 123 bpm |
| 50 | 170 bpm | 102 bpm | 119 bpm |
| 55 | 165 bpm | 99 bpm | 116 bpm |
| 60 | 160 bpm | 96 bpm | 112 bpm |
The Five Heart Rate Zones
Zone 2 doesn't exist in isolation — it's one of five training zones, each targeting different energy systems. The diagram below shows where Zone 2 sits and how it compares to the rest.
What Does Zone 2 Feel Like?
Heart rate monitors are the most reliable way to confirm you're in Zone 2. But the talk test is a good low-tech check: you should be able to say a full sentence without cutting it short to breathe. If you're only managing a few words at a time, you've drifted into Zone 3.
- You can hold a full conversation. The clearest zone 2 marker — speak a complete sentence mid-effort. If you're choppy or gasping between words, ease off immediately.
- Nasal breathing stays comfortable. Most people can breathe through their nose at Zone 2 intensity. If you need your mouth open just to keep up, your pace is too fast.
- Perceived effort sits at 3–4 out of 10. It feels noticeable but far from uncomfortable. Finishing a 45-minute session without feeling wrecked is normal — that's not a sign you didn't work hard enough.
- You could keep going for 90 minutes or more. Zone 2 is defined partly by its sustainability. If the pace forces you to stop after 30 minutes, it wasn't Zone 2.
- Your smartwatch stays in the target window. Trust the number, not the feeling. What feels easy to a sedentary person may already be Zone 3. What feels moderate to a trained runner may be Zone 2 — at a faster pace.
Why Zone 2 Training Works
Zone 2 sits at the intensity where your body draws primarily on fat for fuel and relies on your slow-twitch muscle fibres — the fibres with the highest mitochondrial density. Regular Zone 2 training drives four adaptations that compound over months:
| Adaptation | What it means in practice |
|---|---|
| Mitochondrial density | More mitochondria per muscle cell → greater aerobic capacity at every pace, not just easy ones |
| Fat oxidation | Your body becomes more efficient at burning fat as fuel, sparing glycogen for when you actually need it at hard intensities |
| Cardiac stroke volume | Your heart moves more blood per beat — over time, resting heart rate drops and max cardiac output rises |
| Lactate clearance | Trained aerobic fibres help clear lactate produced during harder efforts, effectively raising your threshold without threshold training |
The key insight is that these adaptations happen without the recovery burden of Zones 3–5. You can accumulate Zone 2 volume day after day in a way that's simply not possible at higher intensities — which is why it produces results that harder training can't replicate.
How Much Zone 2 Per Week?
For recreational athletes, the research-backed sweet spot is 3–5 hours of Zone 2 per week. Elite endurance athletes often log 8–12 hours. In the 80/20 framework — where 80% of total training volume is easy and only 20% is hard — Zone 2 makes up the bulk of that easy 80%.
Any aerobic activity counts — running, cycling, rowing, swimming, hiking, or even a brisk walk if that's where your heart rate falls. Start with two or three 30–45 minute sessions and build from there. Consistency over weeks and months matters far more than any single session.
Frequently Asked Questions
What's the difference between Zone 2 and the "fat-burning zone"?
They describe the same intensity from different angles. The "fat-burning zone" became popular in the 1990s because at Zone 2 intensity your body uses fat as its primary fuel. Zone 2 is the modern, more precise framing — it describes the heart rate band and the physiological adaptations it targets, rather than just the fuel source. The numbers are the same: 60–70% of max HR.
My heart rate creeps above Zone 2 on hills — what should I do?
Slow down or walk the hill. In Zone 2 training the target is heart rate, not pace. Let the terrain dictate your speed, not the other way around. Walk the uphills if that's what it takes to keep your HR in zone. As your aerobic fitness improves over weeks and months, you'll naturally be able to hold the same heart rate at a faster pace — on hills included.
Can I do Zone 2 training by walking?
Yes — especially for beginners or people returning to fitness after a break. A brisk walk often puts untrained individuals squarely in Zone 2. There's nothing wrong with that. As your fitness improves, you'll need to jog to reach the same heart rate. That progression is the whole point: the zone stays the same, the pace required to reach it increases.
How long before Zone 2 training shows results?
Most people notice improved endurance and faster recovery within 6–8 weeks of consistent Zone 2 training. The deeper aerobic base adaptations — measurable improvements in mitochondrial density and fat oxidation — typically take 3–6 months of regular training to fully develop. This is a long game, not a quick fix, which is why consistency matters far more than any individual session.
Should I use the simple formula or the Karvonen method?
If you're just starting out, the simple formula (60–70% of 220 − age) is fine as a starting point. If you're regularly active and have a lower resting heart rate — say, under 60 bpm — use the Karvonen method. It gives a higher, more accurate Zone 2 ceiling, which prevents trained athletes from working at intensities that are too easy to produce meaningful adaptation. The calculator above runs both calculations simultaneously so you can compare.