β€οΈ Karvonen Formula Calculator
Training zones from your heart rate reserve.
For informational purposes only, not medical advice. Consult a healthcare professional.
The Karvonen formula personalizes training zones with your heart rate reserve: max HR minus resting HR. Target HR equals reserve times intensity plus resting HR. Two people with the same max HR but different resting rates get different zones, which matches reality: the fitter heart does the same work at fewer beats.
Enter age and resting heart rate. The calculator estimates max HR, computes your reserve, and lays out all five training zones. Measure resting HR first thing in the morning, before coffee, for the cleanest number.
How to Use This Calculator
Take resting heart rate lying down right after waking, ideally averaged over three mornings. Enter it with your age. Read the five zones and train to the one matching your session goal: recovery, fat burn, cardio, threshold, or max. Re-test resting HR every few months; as fitness improves, zones shift.
Measure resting HR on three calm mornings and average them.
Enter age and resting HR.
Read all five Karvonen zones.
Pick the zone matching today's workout goal and recheck resting HR as fitness changes.
The Karvonen Formula
Max HR = 220 - age
Karvonen, Kentala, and Mustala published the method in 1957, and its insight was the reserve: a percentage of the working range rather than a percentage of the max. Fifty percent of max HR is barely a warmup for most people, but 50% of reserve plus resting lands in a genuinely easy training zone. The 220-minus-age max estimate is the weak link, off by 10 to 15 beats in many individuals; a lab or field test of true max HR sharpens every zone. Tanaka's 208 - 0.7 x age formula estimates max slightly better on average, but Karvonen's structure matters more than which max estimate feeds it.
Worked Example
At 35 with a resting HR of 62: max HR estimates to 185, heart rate reserve is Max HR ~185 - HRR 123, and the fat-burn zone lands at 136 to 148 bpm. Zone 3 cardio runs 148 to 160 bpm, and zone 5 tops out at 173 to 185 bpm. A fitter person with a resting HR of 50 would see every zone shift downward by about 12 beats, which is the whole point of using reserve instead of max alone.
Training to the Zones
Zone 1 (50-60%) is recovery: easy spins and walks that speed repair. Zone 2 (60-70%) is the aerobic base where most endurance training belongs; you can talk in full sentences here. Zone 3 (70-80%) is steady cardio, comfortably hard. Zone 4 (80-90%) is threshold work you can hold for 20 to 60 minutes. Zone 5 (90-100%) is short intervals only. Beginners should live mostly in zones 1 and 2 for the first two to three months; jumping into zone 4 too early is the classic route to burnout and injury.
| Zone | Intensity | Feels like |
|---|---|---|
| 1 Recovery | 50-60% | Easy, nasal breathing |
| 2 Fat burn | 60-70% | Can talk freely |
| 3 Cardio | 70-80% | Talk in phrases |
| 4 Threshold | 80-90% | A few words only |
| 5 Max | 90-100% | Cannot talk |
Heart Conditions Change the Rules
Beta blockers, calcium channel blockers, and several other drugs blunt heart rate, which breaks the formula: zones computed from an unmedicated estimate will overshoot. Heart disease, hypertension, and post-cardiac-event exercisers should get zones from a supervised stress test, not a calculator. Chest pain, faintness, or unusual breathlessness during exercise always deserve prompt medical attention. For informational purposes only, not medical advice. Consult a healthcare professional.
Related tools: heart rate zones calculator, target heart rate and max heart rate.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the Karvonen formula?
Target HR = (max HR minus resting HR) times intensity plus resting HR. It personalizes zones using your heart rate reserve instead of max alone.
What is heart rate reserve?
Max heart rate minus resting heart rate: your working range. A bigger reserve means a fitter cardiovascular system at the same age.
How do I find my max heart rate?
220 minus age is the rough estimate. A graded exercise test measures it directly and is worth doing if you train seriously.
What is the fat-burning zone?
Roughly 60 to 70% of heart rate reserve. You do burn a higher share of fat here, but total calories matter more for fat loss than the zone.
Why are my zones different from my friend's?
Resting HR differs with fitness, so the same age can produce very different zones. That personalization is exactly what Karvonen adds.
Do beta blockers affect Karvonen zones?
Yes, they lower heart rate across the board, so formula-based zones overshoot. Get zones from a supervised test if you take rate-controlling drugs.
How often should I retest resting HR?
Every 2 to 3 months, or after a training block. A falling resting HR means improving fitness and shifting zones.
Is 220 minus age accurate?
Approximately, with errors of 10 to 15 beats common. It is fine for general training and shaky for precise interval prescription.