Heart rate zones explained

Training zones group workout intensity by heart rate so you can pace easy runs, tempo sessions, and intervals without guessing. Sports watches and gym cardio machines often show “Zone 2” or “80% max HR” — this guide explains what those numbers mean and how our calculator estimates them.

Max heart rate estimate

The simplest model is max HR ≈ 220 − age. It is a population average, not a personal test result. A 35-year-old gets an estimated max of 185 bpm; a 50-year-old gets 170 bpm. Lab or field tests (ramp test, recent race effort) can refine this, but the formula is enough for general training bands.

Heart-rate reserve (Karvonen)

Resting pulse matters too. Heart-rate reserve = max HR − resting HR. The Karvonen method targets a percentage of that reserve, then adds resting HR back:

Target HR = (max − resting) × intensity + resting

Someone with max 185 and resting 60 has reserve 125. At 70% intensity: 125 × 0.70 + 60 ≈ 148 bpm. The same percentage of max HR alone would give 130 bpm — Karvonen usually feels more accurate for fit people with low resting pulse.

Zones used on this site

Our Heart Rate Zones calculator shows bands from moderate to maximum effort using reserve percentages:

• Zone 2 (60–70%): Easy aerobic work — conversation pace, fat oxidation, base building.
• Zone 3 (70–80%): Moderate — steady tempo, still sustainable for long stretches.
• Zone 4 (80–90%): Hard — lactate threshold neighbourhood, shorter intervals.
• Zone 5 (90–100%): Very hard — short bursts, near max effort.

Different coaches and devices split zones differently (five zones, seven zones, % of max only). Treat labels as guides, not medical prescriptions.

Worked example

Age 40, resting 58 bpm → max ≈ 180, reserve 122. Zone 2 spans roughly 60–70% of reserve: 131–143 bpm. Zone 4 roughly 156–168 bpm.

FAQs

Should I use wrist optical HR or a chest strap?

Chest straps are usually more stable during intervals; wrists are fine for easy steady runs.

Do medications change zones?

Beta-blockers and some heart medicines lower achievable heart rate. Follow clinician advice rather than generic charts.

Is max HR the same for cycling and running?

Often within a few beats, but sport-specific tests can differ slightly.

Sources

Karvonen et al.; American College of Sports Medicine training guidelines; standard 220−age heuristic.