Heart Rate Zone Formula (Karvonen)
Karvonen's reserve formula uses resting heart rate as a personalization anchor, which is more accurate than the basic %HRmax. Zone 2 — 60–70% of heart-rate reserve — is the aerobic-base workhorse.
Formula
Copy the exact expression or work through it step by step below.
target_HR = (HRmax − HRrest) × intensity_pct + HRrest
HRmax (Tanaka 2001) = 208 − 0.7·age Variables
target_HR
Target heart rate
Beats per minute. The middle of a training zone for the intensity prescribed.
HRmax
Maximum heart rate
BPM. Tanaka 2001 formula: 208 − 0.7·age. More accurate than the legacy 220 − age, especially for over-40s.
HRrest
Resting heart rate
BPM, measured first thing in the morning before getting up, after at least 5 minutes lying still. Average 3–5 days.
intensity_pct
Intensity percentage
Decimal. Zone 1 (recovery): 0.50–0.60; Zone 2 (aerobic base): 0.60–0.70; Zone 3 (tempo): 0.70–0.80; Zone 4 (threshold): 0.80–0.90; Zone 5 (VO₂max): 0.90–1.00.
Step By Step
- 1
Estimate HRmax. Tanaka 2001 (208 − 0.7·age) is the strongest population estimate. A measured max test is more accurate when available.
Age 30: HRmax = 208 − 0.7·30 = 187 BPM.
- 2
Measure resting heart rate over several mornings.
5-day morning average: 58 BPM.
- 3
Compute heart rate reserve: HRmax − HRrest.
187 − 58 = 129 BPM reserve.
- 4
Apply the intensity percentage and add HRrest back. For Zone 2 use 0.60 to 0.70.
60% Z2 floor: 129 × 0.60 + 58 = 135 BPM. 70% Z2 ceiling: 129 × 0.70 + 58 = 148 BPM. Zone 2 = 135–148 BPM.
Worked Example
30-year-old, HRrest 58, Zone 2 target
Age
30
Resting HR
58
Zone
Zone 2 (60–70% HRR)
HRmax = 187. HRR = 129. Z2 floor = 0.60·129 + 58 = 135. Z2 ceiling = 0.70·129 + 58 = 148.
Zone 2: 135–148 BPM. Aerobic base work — should be able to hold a conversation. Most easy runs and the bulk of marathon training live here.
Common Variations
Try These Tools
Run the numbers next
Zone 2 Heart Rate Calculator
Calculate your Zone 2 heart rate with Maffetone, Karvonen, % Max HR, and lactate threshold methods compared side by side.
VO2 Max Estimator
Estimate aerobic capacity with Cooper run, Rockport walk, or no-exercise questionnaire methods.
Sources & References
- Tanaka H et al. Age-predicted maximal heart rate revisited — Journal of the American College of Cardiology (2001)
- Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study — Annales Medicinae Experimentalis et Biologiae Fenniae (1957)