How this instrument works
This calculator answers a narrow, practical question: what one heart-rate number should I aim for right now? Enter a maximum heart rate, a resting heart rate, and a single intensity percentage, and it returns a single target in beats per minute — useful when you just want a number to glance at on a watch during a session, rather than a full range to stay inside.
The formula behind it is the Karvonen method, published by M.J. Karvonen and colleagues in 1957: take the gap between maximum and resting heart rate (called heart rate reserve), multiply by the chosen intensity percentage, then add resting heart rate back on. Because resting heart rate factors into the result, two people sharing an identical maximum pulse but differing in fitness — and therefore in resting pulse — get different targets for the same intensity percentage, which a flat percentage of maximum alone can't do.
This site also has two close relatives built on the exact same formula: a Heart Rate Zone calculator that takes a low and high percentage and returns a full training range instead of one number, and a dedicated Karvonen Formula calculator (in the health section) that goes deep on the method's 1957 origin and how it compares to the well-known 220-minus-age heart-rate estimate. This page is the quick, single-number version of that same math.
- Enter Maximum heart rate — from a measured max-effort test, a wearable's recorded peak, or an estimate from this site's max-heart-rate calculator.
- Enter Resting heart rate — ideally measured first thing in the morning before getting out of bed.
- Set Target intensity as a percentage — roughly 50-60% for easy recovery, 60-70% for aerobic base work, 70-85% for tempo effort, 85%+ for hard intervals.
- Read Target heart rate — the single beats-per-minute number to aim for at that intensity.
- Maximum heart rate must be greater than resting heart rate, or the instrument will flag the inputs.
Worked example — max 190, resting 55, 70% effort
Enter a maximum heart rate of 190 bpm, a resting heart rate of 55 bpm, and a target intensity of 70%. Heart rate reserve is 190 - 55 = 135 bpm. Target heart rate is (135 x 0.70) + 55 = 94.5 + 55 = 149.5 bpm.
Drop the intensity to a gentler 60% with a slightly different max and resting pair — max 180, resting 65 — and the target moves to (115 x 0.60) + 65 = 69 + 65 = 134 bpm, a full 15.5 beats lower, driven entirely by the lower intensity fraction and the different max/resting starting point.
Questions
What intensity percentage should I pick for my target?
Roughly 50-60% suits easy recovery sessions, 60-70% suits comfortable aerobic base-building, 70-85% covers tempo or threshold work, and above 85% is typically reserved for short, hard interval efforts. These bands are common coaching convention rather than a strict rule, so treat them as a starting point and adjust based on how sessions feel and how well you recover.
Where do I get my maximum and resting heart rate numbers?
Maximum heart rate ideally comes from a supervised max-effort test or a genuinely hard race/interval recorded on a chest strap; this site's max-heart-rate calculator offers a quick age-based estimate if you don't have a measured figure. Resting heart rate is most accurate measured first thing in the morning, before sitting up, ideally averaged over a few consecutive days.
Why use heart rate reserve instead of a flat percentage of my maximum?
Because maximum alone doesn't reflect fitness. Two people can share an identical top-end pulse while sitting at very different fitness levels, and a flat percentage of maximum would hand them the same target regardless — folding in resting heart rate, a rough fitness proxy, gives each person a more individually calibrated number for the same intensity fraction.
Is this the same as the Heart Rate Zone calculator on this site?
Yes, identical formula — the difference is the output shape. This page takes one intensity percentage and returns one target number, handy when you just want a single figure to aim for. The Heart Rate Zone calculator takes a low and a high percentage and returns a full range instead, better suited to staying inside a band throughout a longer or mixed-pace session.
Is this the same as the dedicated Karvonen Formula calculator?
Same underlying math, yes — this site's Karvonen Formula calculator, in the health section, uses the identical heart-rate-reserve formula but is built around a deeper look at the method's history and how it stacks up against the common 220-minus-age heart-rate estimate. This page is the streamlined version, scoped to quickly producing one training target.