What heart rate zones are (and why people use them)

Heart rate zones are a practical way to estimate training intensity. Your heart rate rises as your effort rises. If you can keep your effort inside a specific range — say “Zone 2” — you can roughly repeat the same workout feeling across different days, even when pace, incline, weather, or fatigue changes.

Zones are especially popular because they’re simple to track (watch, treadmill, chest strap) and easy to explain: low zones feel easy and sustainable; high zones feel hard and are best used in short doses. That makes zones useful for: building aerobic fitness, improving endurance, managing recovery, pacing long runs, structuring HIIT, and preventing the classic mistake of going “too hard on easy days and too easy on hard days.”

This calculator gives you five zones. There are other systems (3 zones, 6 zones, sport-specific zones), but the 5-zone model is the easiest to understand, and it matches what most fitness apps and watches display. Think of it as a “good default” for people who want a clear target.

• Zone 1 (Very easy): warm-ups, cool-downs, recovery walks/jogs. You can hold a full conversation.
• Zone 2 (Easy): comfortable endurance work (“base”). You can talk in full sentences.
• Zone 3 (Moderate): steady cardio. Talking becomes shorter phrases.
• Zone 4 (Hard): threshold/tempo intervals. Talking is difficult.
• Zone 5 (Very hard): sprints and short bursts. Talking is basically not happening.

You’ll see Zone 2 all over TikTok, YouTube, and running/cycling communities because it’s a sweet spot for consistent progress. It’s low enough that you can do more volume without burning out, but high enough to stimulate aerobic improvements. It’s not magic — it’s just a sustainable intensity you can repeat. That repeatability is the whole game.

How this calculator computes your zones

Step 1 is estimating your maximum heart rate (Max HR). This calculator offers a few common age-based formulas. Age-based formulas are imperfect (two people of the same age can have very different true max HR), but they’re good enough for a starting estimate.

• Classic: Max HR ≈ 220 − age
• Tanaka: Max HR ≈ 208 − 0.7×age
• Gellish: Max HR ≈ 207 − 0.7×age
• Gulati (often cited for women): Max HR ≈ 206 − 0.88×age

Once Max HR is estimated, each zone is a percentage band of Max HR. This calculator uses the popular 5-zone split: Zone 1: 50–60%, Zone 2: 60–70%, Zone 3: 70–80%, Zone 4: 80–90%, Zone 5: 90–100%.

If you enter a resting heart rate, the Karvonen method adjusts targets using your usable heart rate range. First compute HRR = Max HR − Resting HR. Then each zone becomes: Target HR = Resting HR + (HRR × zone%). Many people find HRR-based zones match perceived effort better, especially if their resting HR is unusually low (very fit) or higher than average.

Example calculations (so you can sanity-check)

These examples show the math end-to-end so you can confirm the calculator outputs look reasonable. (Remember: these are estimates. Your watch, lab test, or doctor may give different individualized targets.)

Max HR ≈ 220 − 30 = 190 bpm. Zone 2 (60–70%) ≈ 0.60×190 to 0.70×190 = 114–133 bpm. Zone 4 (80–90%) ≈ 152–171 bpm.

Max HR ≈ 220 − 40 = 180 bpm. HRR = 180 − 60 = 120. Zone 2 (60–70% HRR): 60 + 0.60×120 to 60 + 0.70×120 = 132–144 bpm. Zone 5 (90–100% HRR): 60 + 108 to 60 + 120 = 168–180 bpm.

Two people can have the same Max HR estimate but different resting HR (say 48 vs 72). HRR will give the person with a lower resting HR slightly lower easy-zone numbers and can shift zone boundaries in a way that matches “easy feels easy” more accurately.

How to use your zones in real workouts

The most practical way to use zones is to match them to workout types. Here’s a simple mapping that works for most people:

• Warm-up / Cool-down: Zone 1
• Easy base cardio: Zone 2 (steady, repeatable)
• Moderate steady cardio: Zone 3 (not daily for beginners)
• Tempo / threshold blocks: Zone 4 (shorter intervals)
• Sprints / hard intervals: Zone 5 (very short bursts)

• 3×/week: 30–45 min Zone 2
• 1×/week: Zone 4 intervals (example: 4×4 minutes hard with easy recovery)
• Daily: optional Zone 1 walk for recovery and steps

Reality check: heart rate lags behind effort (especially in intervals). For short sprints, use “effort” + pace/power guidance too.

Frequently Asked Questions

• Which method should I choose: %Max HR or Karvonen?

  If you want quick and simple, use %Max HR. If you know your resting HR and want a more individualized estimate, use Karvonen (HRR). Many people prefer HRR because it adjusts for fitness differences reflected in resting heart rate.

• Are these zones scientifically perfect?

  No. Age-based Max HR formulas and generic zone splits are estimates. They’re still useful because they give you a repeatable target. If you want precision, you’d use lab testing, sport-specific field tests, or clinician guidance.

• My watch shows different zones. Which is correct?

  Watches often use their own Max HR estimates (sometimes learned from workouts) and different zone definitions. What matters most is consistency: pick one system and use it to guide training over time.

• Why does my heart rate drift upward during easy cardio?

  That’s normal (cardiac drift), especially with heat, dehydration, fatigue, or long sessions. If you want to stay in a zone, you may need to slightly reduce pace later in the workout.

• Can I use this for walking?

  Yes. Many people use Zone 1–2 targets for brisk walking. If your heart rate climbs too quickly, reduce incline or pace.

• Is “fat-burning zone” real?

  Lower intensity tends to use a higher proportion of fat as fuel, but total fat loss depends on overall energy balance. Zone 2 is popular because it’s sustainable and supports doing more total work over time.