Is Heart Rate Zones free and safe to use?

Heart Rate Zones is free and runs directly in your browser, so you can use it instantly without installing software.

Heart Rate Zones

Calculate your personalized heart rate training zones using the Karvonen formula. Enter your age and resting heart rate to get 5 color-coded zones for recovery, fat burn, aerobic, anaerobic, and VO₂ max training.

Your Details

Age (years)

Resting Heart Rate (bpm)

Measure in the morning before getting out of bed.

190

Max HR (220 − age)

120

HR Reserve

Karvonen Formula:
Target HR = ((Max HR − Resting HR) × Intensity%) + Resting HR
Source: Karvonen MJ et al, 1957

Training Zones

Zone 1 — Recovery

Light effort, active recovery, warm-up/cool-down

130–142 bpm

50–60% intensity

Zone 2 — Fat Burn

Comfortable pace, fat oxidation, endurance base

142–154 bpm

60–70% intensity

Zone 3 — Aerobic

Moderate effort, cardiovascular fitness

154–166 bpm

70–80% intensity

Zone 4 — Anaerobic

Hard effort, lactate threshold, speed training

166–178 bpm

80–90% intensity

Zone 5 — VO₂ Max

Maximum effort, short bursts, peak performance

178–190 bpm

90–100% intensity

Training Guidelines

Endurance

Zone 2 — 142–154 bpm

80% of weekly training volume

Tempo

Zone 3 — 154–166 bpm

10% of weekly training volume

Intervals

Zone 4-5 — 166–190 bpm

10% of weekly training volume

What is Heart Rate Zones Calculator?

The Karvonen Formula (1957) calculates target heart rate zones using your Heart Rate Reserve (HRR) — the difference between your maximum and resting heart rates. This method is recommended by the American College of Sports Medicine (ACSM) because it accounts for individual fitness levels.

The formula: Target HR = ((Max HR − Resting HR) × Intensity%) + Resting HR, where Max HR = 220 − Age. This calculator provides 5 standard training zones: Zone 1 (Recovery, 50-60%), Zone 2 (Fat Burn, 60-70%), Zone 3 (Aerobic, 70-80%), Zone 4 (Anaerobic, 80-90%), Zone 5 (VO₂ Max, 90-100%). All calculations run locally in your browser.