Heart Rate Reserve (HRR) Calculator — Karvonen Formula
Calculate your heart rate reserve and your 5 training zones with the Karvonen formula (or % of HRmax)
Your heart rate data
Measured in the morning, lying down, for 1 minute
Your 5 heart rate zones
Overview
Your calculation, step by step
- 1. Heart rate reserve = 190 − 60 = 130 bpm
- 2. Zone 2 lower limit (60 % HRR) = 130 × 0.60 + 60 = 138 bpm
- 3. Zone 2 upper limit (70 % HRR) = 130 × 0.70 + 60 = 151 bpm
So your easy aerobic runs sit between 138 and 151 bpm. Every other zone is computed the same way with its own percentages.
Your zones are ready. Now what?
A training plan that tells you what to do in each zone: easy runs, threshold, intervals — all calibrated to your heart rate.
Understanding aerobic endurance
Zone 2 is the key to running progress. Discover why 80% of your training should be done at easy aerobic effort.
Read our complete guide on fundamental enduranceWhat is a heart rate zone?
Heart rate zones are intensity ranges defined as a percentage of your maximum heart rate (HRmax) or heart rate reserve (HRR). They help structure your training by targeting specific physiological adaptations: recovery, aerobic endurance, lactate threshold, or maximal power. Knowing your zones is essential for effective progress while avoiding overtraining.
How to calculate heart rate reserve
Heart rate reserve (HRR) is the gap between your maximum heart rate and your resting heart rate: HRR = HRmax − resting HR. Example: with an HRmax of 190 bpm and a resting HR of 60 bpm, your HRR is 130 bpm. It is the range of beats actually available for effort, and it is what the Karvonen formula applies its percentages to. Two runners with the same HRmax but different resting heart rates therefore get different zones: the lower the resting HR, the bigger the reserve. Enter your two values above and the calculator gives you your HRR and your five zones instantly.
Karvonen formula explained
The Karvonen formula turns your heart rate reserve into training zones: target HR = (HRR × % intensity) + resting HR. With a 130 bpm reserve and a 60 bpm resting HR, 60 % gives 130 × 0.60 + 60 = 138 bpm and 70 % gives 151 bpm — that is your zone 2. It is more accurate than a plain % of HRmax because it accounts for your fitness level, reflected by your resting heart rate. A trained runner with a low resting HR gets slightly different zones than a beginner with the same HRmax.
How to measure your maximum heart rate?
The most reliable method is a lab stress test. Alternatively, you can do a field test: after a 15-minute warm-up, run 3 × 3 minutes at maximum intensity with 2 minutes recovery. Your highest recorded HR will be close to your HRmax. The Tanaka formula (208 - 0.7 × age) gives an estimate, but individual variation is significant (±10 bpm). Measure your resting HR in the morning, lying down, for 1 minute.
Frequently asked questions
What's the difference between Karvonen and %HRmax?
The Karvonen method uses your HR reserve (HRmax - resting HR) and gives more precise zones as it accounts for your fitness. The %HRmax method is simpler (direct % of HRmax) but less personalized. If you know your resting HR, prefer Karvonen.
How do I find my maximum heart rate?
A lab stress test is the gold standard. In practice, a field test (3 × 3 min all-out after warm-up) or the Tanaka formula (208 - 0.7 × age) give a good approximation. Note: the formula can vary by ±10 bpm between individuals.
Which zone should I run in most often?
Most of your training (70-80%) should be in zone 2 (aerobic endurance). This zone builds your aerobic base, improves fat utilization, and allows recovery while progressing. Zones 4-5 represent 10-20% for quality sessions.
Why is my resting heart rate important?
Resting HR reflects your cardiovascular fitness. The lower it is, the more efficient your heart. It allows the Karvonen method to personalize your zones. It naturally decreases with training: a regular runner can reach 45-55 bpm.