Example Data Table
| Age | Resting HR | HRmax Method | Zone Model | Estimated HRmax | Endurance Zone (Zone 2) |
|---|---|---|---|---|---|
| 30 | 60 | Tanaka | Percent of HRmax | 187 bpm | 112–131 bpm |
| 45 | 58 | Fox | Karvonen (HRR) | 175 bpm | 128–139 bpm |
Formula Used
1) HRmax estimation options
Fox: HRmax = 220 − age
Tanaka: HRmax = 208 − 0.7×age
Gellish: HRmax = 207 − 0.7×age
Custom HRmax uses your provided tested value.
2) Zone calculation models
Percent of HRmax:
Zone bpm = HRmax × (intensity%)
Karvonen (HRR):
HRR = HRmax − HRrest,
Target bpm = HRrest + HRR × (intensity%)
3) Endurance zone definition (Zone 2)
This calculator uses 60–70% intensity for Zone 2.
It is a practical aerobic baseline for steady training sessions.
How to Use This Calculator
- Enter your age, and your resting HR if known.
- Select a zone model. Use HRR for more personalization.
- Choose an HRmax method, or enter a tested custom HRmax.
- Press Calculate Zones to display results above the form.
- Use the Zone 2 range for long steady sessions and base building.
- Download the zone table as CSV or PDF for logs and plans.
Why Endurance Zones Matter
Endurance work builds aerobic capacity by stressing mitochondria, capillary density, and fat oxidation. Most athletes place steady sessions in the 60–75% range of maximum heart rate, which the calculator shows as Zone 2. Zone 3 typically sits around 75–85% and supports tempo durability. Tracking these ranges reduces “junk miles” and keeps easy days truly easy. For runners, pace varies with hills, so heart-rate zones standardize effort across terrain and fatigue.
Inputs That Improve Zone Accuracy
Using a measured resting heart rate and a realistic maximum heart rate improves zone boundaries. If you know a lab-tested lactate threshold, you can compare it with the top of Zone 3 to sanity-check results. Age formulas are a starting point, but field tests often shift HRmax by ±10–15 bpm. The calculator lets you store unit preferences and include a safety buffer when you are returning after illness.
Interpreting Zone 2 and Zone 3
Zone 2 should feel conversational, roughly RPE 2–4 on a 10-point scale, with breathing controlled and cadence stable. Zone 3 feels “comfortably hard” at about RPE 5–6, where full sentences become difficult. If your heart rate drifts upward more than 5% at the same pace, you are likely under-fueled, dehydrated, or overheating. Use the displayed ranges to cap intensity rather than chase a target number.
Training Volume Targets and Progression
For general fitness, aim for 120–240 minutes per week in Zones 1–2, split into 3–5 sessions. Endurance athletes commonly allocate 70–80% of weekly time to Zones 1–2, 15–25% to Zone 3, and a small remainder to higher zones. Increase weekly volume by 5–10% and add recovery every 3–4 weeks. The calculator’s export options help you log zones alongside distance and duration. Add one long session of 45–90 minutes each week, staying under the upper cap displayed.
Common Errors and Quality Checks
Errors usually come from stale HRmax estimates, caffeine spikes, or wrist-sensor lag. Re-test HRmax or threshold each 8–12 weeks, and update inputs when your fitness changes. Prefer chest-strap readings for interval-heavy days and compare average and peak values. If numbers look off, rerun the calculator with an adjusted buffer and confirm using the talk test.
FAQs
Zone 2 is calculated at 60–70% intensity using either percent-of-HRmax or Karvonen HRR. Sub-ranges split the band so you can stay comfortably aerobic.
If you know your resting heart rate, HRR usually personalizes zones better, especially for trained athletes. If resting HR is unknown, percent-of-HRmax is a reasonable baseline.
Devices may use different zone definitions or smoothing. Keep your method consistent: update your inputs, then compare trends over time rather than chasing exact bpm matches.
Recheck after major fitness changes, or every 8–12 weeks during structured training. If you complete a hard test that reveals a higher peak, update the calculator to avoid underestimating zones.
Yes. Heart-rate zones translate across endurance sports, but mechanical load differs. For hot conditions or hills, use the upper cap to prevent drifting into higher effort.
Use the talk test and perceived exertion: you should speak in full sentences, breathe rhythmically, and recover quickly. If breathing becomes labored, drop intensity until you return to the target band.