Free cardio calculator
Heart-rate zone calculator
Estimate five training zones using heart-rate reserve, resting heart rate, and measured or age-predicted maximum heart rate.
Reviewed February 19, 2026
Tanaka predicted max
184 bpm
Heart-rate reserve
124 bpm
General estimate only. Medications and health conditions can change heart-rate response; seek clinical guidance when appropriate.
What this result means
This calculator uses the Karvonen heart-rate-reserve method: subtract resting heart rate from maximum heart rate, multiply by the zone intensity, then add resting heart rate back. A measured maximum is more individual than an age prediction.
Target HR = ((max HR − resting HR) × intensity) + resting HR.
Why formulas disagree
Some systems use percentages of maximum heart rate; others use heart-rate reserve or lactate threshold. Their zone numbers are not interchangeable.
Age-predicted maximum heart rate describes a population trend and can be far from an individual’s actual maximum.
Use zones with effort cues
Heart rate responds to heat, dehydration, stress, medication, fatigue, and sensor error. Pair the number with breathing, conversation, pace, and how the session feels.
This tool is for general education, not diagnosis or exercise clearance. Discuss health concerns and medication effects with a qualified clinician.
Frequently asked questions
What is the Karvonen method?
It calculates target heart rate from heart-rate reserve, which is maximum heart rate minus resting heart rate.
Is 220 minus age accurate?
It is a rough population estimate and may differ substantially from an individual’s measured maximum.
What is Zone 2?
The label depends on the zone system. In this five-zone HRR model, Zone 2 is 60–70% of heart-rate reserve plus resting heart rate.
Sources and assumptions
Zones need context
Pair the estimate with pace and perceived effort.
LogFast helps you keep heart-rate context alongside duration, pace, and how the session felt—without pretending one zone formula knows your body perfectly.
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