Heart Rate Zone Calculator Comparison

Different calculators use different methods to determine heart rate zones, leading to significant variations in Zone 2 ranges. This tool compares popular methods side-by-side so you can see how much they differ and choose the best approach for your training.

Note: This tool is for educational purposes only. Consult with a healthcare professional before starting any new exercise program. For most accurate results, get your max heart rate and threshold tested in a lab.

Age (required)

Resting Heart Rate (optional, for Karvonen)

Tested Max Heart Rate (optional)

Functional Threshold HR (optional, for Friel)

VO2 Max (optional, for Daniels - requires Max HR or Age)

Zone 2 Comparison Results

Method	Inputs Used	Max HR	Zone 2 Range	Description

Why Do Results Vary So Much?

Heart rate zone calculations vary because they use different formulas for estimating max heart rate and different percentage ranges for defining zones. Age-based formulas like "220 - age" are simple but can be off by 10-20 bpm. Threshold-based methods require testing but are more accurate for trained athletes. Watch manufacturers typically use simpler age-based formulas for convenience.