Estimated max HR = 220 − age. Heart-rate reserve = max HR − resting HR. Target low = reserve × low % + resting HR. Target high = reserve × high % + resting HR.
Worked example
At age 35, estimated max HR is 185 bpm. With resting HR 65, a 60-80% reserve zone is about 137-161 bpm.
Professional note
Master’s Tip: heart-rate reserve usually gives a more personal zone than simply taking a percent of max heart rate.
Regional and unit assumptions
General fitness estimate using the Karvonen heart-rate-reserve method.
Assumptions and limitations
Maximum heart rate formulas are approximate.
Medical conditions, medication and fitness level can change safe training intensity.
Stop exercise and seek help for chest pain, fainting or severe symptoms.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Estimated max HR = 220 − age. Heart-rate reserve = max HR − resting HR. Target low = reserve × low % + resting HR. Target high = reserve × high % + resting HR.
Standard or basis
General fitness estimate using the Karvonen heart-rate-reserve method.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.
Master's Tip
Master’s Tip: heart-rate reserve usually gives a more personal zone than simply taking a percent of max heart rate.
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