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HealthNot all exercise is equal — a gentle walk and an all-out sprint trigger completely different adaptations in your body. Heart rate zones turn that spectrum into five numbered bands, so every workout can target a specific goal: recovery, fat metabolism, endurance, speed, or power.
This guide explains the five zones, how to calculate yours, and which zone belongs in your training week.
Try it yourself: Plan training with precise pace math. Pace Calculator →
First: your max heart rate
Every zone is a percentage of your maximum heart rate (MHR) — the fastest your heart can beat during all-out effort. The classic estimate:
MHR ≈ 220 − age
— a 40-year-old: 180 bpm —
— a 40-year-old: 180 bpm —
This is a population average with real individual variation (±10–15 bpm). A newer formula, 208 − 0.7 × age, fits older adults slightly better. For serious training, a field test (a hard time-trial effort observed on a monitor) beats any formula.
The five zones
| Zone | % of max | Feels like | Training purpose |
|---|---|---|---|
| Zone 1 — Recovery | 50–60% | Easy stroll, can sing | Warm-up, cool-down, active recovery |
| Zone 2 — Aerobic base | 60–70% | Brisk, can hold a conversation | Fat metabolism, endurance foundation |
| Zone 3 — Tempo | 70–80% | Comfortably hard, short sentences | Cardio efficiency, race pace for longer events |
| Zone 4 — Threshold | 80–90% | Hard, one-word answers | Lactate threshold, speed endurance |
| Zone 5 — Maximum | 90–100% | All-out, cannot talk | Top-end power, seconds to minutes only |
For our 40-year-old (MHR 180): Zone 2 is 108–126 bpm, Zone 4 is 144–162 bpm, and Zone 5 starts at 162 bpm.
The Karvonen refinement
The Karvonen formula personalizes zones using your resting heart rate (measure it first thing in the morning):
Target = ((MHR − resting HR) × %intensity) + resting HR
Our 40-year-old with a resting HR of 60 wanting Zone 2 at 65%: ((180 − 60) × 0.65) + 60 = 138 bpm. Two people with the same MHR but different fitness levels get appropriately different targets — that's the point.
Zone 2: the most misunderstood band
Zone 2 earned the nickname "fat-burning zone" because the highest proportion of energy comes from fat there. But proportion isn't total: higher zones burn more calories per minute, so they burn more fat in absolute terms despite a lower percentage. Zone 2's real value is different — it's where aerobic base is built, it's sustainable for hours, and it's gentle enough for frequent, near-daily sessions. Most endurance coaches assign 70–80% of weekly training time to Zones 1–2.
A sensible weekly mix
- Most sessions: Zone 2 — long, conversational cardio builds the engine.
- One session: Zone 3–4 intervals — tempo runs, hill repeats, threshold sets.
- Occasionally: Zone 5 sprints — short, with full recovery between efforts.
- Recovery days: Zone 1 — easy movement beats the couch, but barely.
If you're new to exercise, have a heart condition, high blood pressure, or take heart-rate-affecting medication, get medical clearance before training by heart rate — and know that medications like beta-blockers make the formulas unreliable.
Frequently asked questions
Zone 1 (50–60% of max) is recovery; Zone 2 (60–70%) builds aerobic base; Zone 3 (70–80%) is tempo/cardio; Zone 4 (80–90%) is lactate threshold; Zone 5 (90–100%) is maximum effort, sustainable only for seconds to a few minutes.
The classic estimate is 220 minus your age. A 40-year-old gets 180 bpm. It is a rough population average with individual variation of ±10–15 bpm — newer formulas like 208 − 0.7 × age are slightly more accurate for older adults.
Zone 2 (60–70% of max) burns the highest proportion of fat, which is why it is nicknamed the "fat-burning zone." But total calories burned matters more for fat loss — higher zones burn more total calories per minute.
For healthy people, short Zone 5 efforts are a normal part of training. But max-effort exercise stresses the cardiovascular system, so anyone with a heart condition, high blood pressure, or who is new to exercise should get medical clearance first.
Disclaimer: Calculator health content is for education only — not medical advice. Body metrics are screening tools, not diagnoses. If you have concerns about your health, speak with a qualified health professional.