Heart rate zone calculator

How to calculate your heart rate zones

1. Enter your age in years. Your max HR and 5 training zones appear instantly using the Tanaka formula.
2. Optionally enter your resting heart rate (measured first thing in the morning) to enable Karvonen personalised zones.
3. Review your 5 zones with bpm ranges and activity descriptions for each.
4. Use Zone 2 for base endurance training and Zone 4–5 for interval sessions.

Common uses

• Setting heart rate targets for a running, cycling, or rowing training programme alongside your calorie targets
• Implementing 80/20 training (80% Zone 1–2, 20% Zone 3–5)
• Calibrating a heart rate monitor or sports watch with personalised zones, alongside a BMI calculator for a baseline fitness snapshot

Technical specification

• Algorithm or formula: Max HR via Tanaka et al. 2001 (208 − 0.7 × age). With resting HR, zones use the Karvonen reserve formula HR_zone = ((HRmax − HRrest) × intensity) + HRrest. Zone intensities span 50 to 100 percent in five bands.
• Browser API or library: Pure JavaScript arithmetic. No external library.
• Input limits: Age in years (positive integer). Resting HR optional, expected 30 to 120 bpm.
• Output: Maximum HR plus five zones with bpm ranges and activity descriptions (recovery, base endurance, aerobic, anaerobic threshold, max effort).
• Known limitations: All max-HR predictions carry roughly ±10 bpm individual variance. A graded exercise test gives a more accurate personal max HR.

Frequently asked questions

What are heart rate training zones?

Training zones are ranges of heart rate corresponding to specific exercise intensities. Zone 1 (50–60% max HR) is recovery; Zone 2 is base endurance; Zone 3 is aerobic/tempo; Zone 4 is anaerobic threshold; Zone 5 is maximum effort. Each zone produces different physiological adaptations.

Is this heart rate calculator completely free?

Yes. No registration, no account, and no payment required.

Do I need an account to use this calculator?

No. Enter your age. Your zones appear instantly. Nothing is stored or uploaded.

What is the difference between the Tanaka and classic 220 minus age formula?

The Tanaka formula (208 − 0.7 × age) was validated in a meta-analysis of 351 studies involving 18,712 subjects (JACC 2001) and is more accurate than the classic 220 − age formula, particularly for adults over 40. Both are shown for comparison.