How this instrument works
The Karvonen method calculates a target heart rate from heart rate reserve — the gap between maximum heart rate (HRmax) and resting heart rate (HRrest) — rather than from HRmax alone. It multiplies that reserve by a chosen intensity percentage, then adds HRrest back, which produces a more personalised target than a simple percentage of maximum, since it accounts for individual fitness through the resting baseline.
For cycling specifically, structured sessions on an indoor trainer or a set of outdoor intervals are commonly prescribed as a percentage of heart rate reserve, because HR on a bike responds a little differently to effort than it does running — cyclists can coast and freewheel, and HR tends to lag behind sudden changes in power more than it does when running at a steady cadence with no freewheeling possible.
Getting useful numbers out of this instrument starts with two honest measurements: HRrest, best taken first thing on waking before getting out of bed, and HRmax, ideally from a supervised field test rather than an age-based formula, since individual variation around any age-based estimate can be substantial. The target intensity percentage then comes from whatever structured training plan or coach is prescribing the session.
- Enter Maximum heart rate (bpm) — from a field test where possible, or a working estimate if a test isn't available.
- Enter Resting heart rate (bpm) — measured on waking, before caffeine or getting out of bed, for the most consistent reading.
- Enter Target intensity (%) — the percentage of heart rate reserve a training plan calls for, from 0 to 100.
- Read Target heart rate (bpm) — the beats-per-minute to hold for that specific intensity.
- Maximum heart rate must be greater than resting heart rate, and intensity must fall between 0 and 100, or the instrument will prompt for a valid value.
- Repeat with a different intensity percentage to find the boundary of each training zone in a structured plan.
Worked example — 75% intensity for a 185/60 rider
Enter 185 into Maximum heart rate (bpm), 60 into Resting heart rate (bpm) and 75 into Target intensity (%) — a rider with a tested max of 185 bpm and a 60 bpm resting HR, aiming for a 75% HR reserve effort, a common tempo-to-threshold training zone. Target heart rate reads 153.75 bpm.
That comes from an HR reserve of 185 − 60 = 125 bpm; 75% of that reserve is 93.75 bpm; adding the 60 bpm HRrest back gives 153.75 bpm. The same rider working a much easier 50% effort would target only (125 × 0.5) + 60 = 122.5 bpm, showing how much the target shifts across a fairly modest change in intensity.
Questions
Why use heart rate reserve instead of a simple percentage of max heart rate?
Because heart rate reserve accounts for individual fitness through the resting baseline, while a simple percentage of maximum treats two riders with very different resting rates identically. Two cyclists sharing the same HRmax but with resting rates of 50 and 70 bpm get noticeably different Karvonen targets at the same intensity percentage, which better reflects how hard that effort actually feels for each of them.
How do I find my true maximum and resting heart rate?
Resting heart rate is straightforward to find — count it first thing on waking, before getting out of bed, ideally averaged over a few mornings. HRmax is harder to get precisely; a supervised field test with a coach or in a lab gives the most reliable figure, since age-based formulas can be off by ten or more beats per minute for a given individual.
What intensity percentage should I use for different cycling zones?
As a rough guide, easy endurance riding often sits around 60-70% of heart rate reserve, tempo work around 70-80%, and threshold intervals push toward 80-90% or higher, but exact zone boundaries vary between training systems and coaches. Whatever percentage a specific training plan calls for, entering it here converts that percentage directly into a beats-per-minute target.
How is this different from the cycling-zones instrument on this site?
This page targets a heart rate in bpm from a chosen intensity percentage of heart rate reserve; cycling-zones instead works out power-based training zones in watts from a rider's Functional Threshold Power. HR and power measure effort differently — power responds instantly to pedalling force, while HR lags behind — so many structured plans use both together rather than relying on just one.
Why does my heart rate lag behind my power on a climb?
HR is a physiological response that takes tens of seconds to catch up with a sudden change in effort, while power output on a bike changes the instant pedalling force changes. That lag is exactly why an HR-only target can undershoot the true effort during a short, hard surge, and why riders training with a power meter often treat power as the more immediate signal, with HR as a slower-moving cross-check.