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Heart Rate Zones: Math for Training, With the Error Bars Shown
Health · 6 min read · Last updated September 2026
Step 1: estimate your maximum heart rate
Tanaka: HRmax = 208 − 0.7 × age
Age 35: Fox gives 185, Tanaka gives 183.5 — close here. At age 60 they diverge: Fox 160, Tanaka 166. Fox's equation came from a scatter of studies and systematically underestimates HRmax in older adults; Tanaka was fitted on a larger measured sample. Neither beats an actual field test (a hard, properly warmed-up effort) or a lab test.
Step 2: cut the range into five zones
Using Tanaka 183.5 bpm for our 35-year-old (reserve method shown because it anchors zones to resting heart rate too: HRR = HRmax − HRrest; zones = HRrest + %×HRR, with HRrest = 60): HRR = 123.5.
| Zone | % of HRmax | Feel | Example bpm (max-%) |
|---|---|---|---|
| Z1 recovery | 50–60% | Easy, conversational | 92–110 |
| Z2 aerobic | 60–70% | Comfortably breathing harder | 110–128 |
| Z3 tempo | 70–80% | "Comfortably hard" | 128–147 |
| Z4 threshold | 80–90% | Hard, short phrases only | 147–165 |
| Z5 VO₂max | 90–100% | All-out, minutes at most | 165–183 |
Most endurance training time belongs in Z1–Z2 — the "80/20" distribution popularized by polarized-training research. Zone 2 mislabeled as Z3 is the most common self-coaching error, and it usually comes from an HRmax formula that underestimates your true max.
Try the calculators
Worked example: Target Heart Rate Zones at its default inputs
Take the default setup on Target Heart Rate Zones: no fields changed, nothing tuned to a nice round number. Run in the site's own engine, those values produce the answer below.
| Input | Default |
|---|---|
| Age | 30 |
| Resting Heart Rate (bpm) | 70 |
Result: Zone: 130–154 bpm
The steps behind that answer
- Step 1: Max HR = 220 − 30 = 190 bpm
- Step 2: Heart rate reserve = 190 − 70 = 120 bpm
- Step 3: Zone = resting + reserve × intensity (Karvonen formula)
- Step 4: moderate zone ≈ 130–172 bpm
What Age does to the answer
Age is the first input worth testing, so here it is at three sizes.
| Age | Result |
|---|---|
| 15 | Zone: 138–165 bpm |
| 30 | Zone: 130–154 bpm |
| 45 | Zone: 123–144 bpm |
Halve age and the result moves one way; add half again and it moves the other. Watching that gap is quicker than guessing which field matters most.
Related guides
The age formula is a population average
The 220 minus age estimate of maximum heart rate has a standard deviation of roughly 10-12 beats per minute. For a 40-year-old, the plausible maximum spans something like 160 to 200, which moves every zone derived from it.
A measured maximum from a field test or a lab is far better if you train seriously. The formula is a placeholder, and zones built on it inherit its error.
Zones as percentages of maximum
Common bands run from 50-60% for recovery, 60-70% for aerobic base, 70-80% for tempo and 80-90%+ for threshold and VO2 work. The boundaries are conventions, not sharp physiological switches.
Heart rate also drifts upward during a long effort at constant pace, from heat and dehydration. Judging effort by pace or power as well as heart rate prevents chasing a number that is moving for reasons unrelated to intensity.
Medication and individual variation
Beta blockers and some other medications lower heart rate directly, which makes any age-based zone wrong. So does a naturally high or low resting rate.
Use perceived effort as a cross-check, and treat chest pain, unusual breathlessness or dizziness as a reason to stop rather than a zone to push through.
Frequently asked questions
Which max heart rate formula should I use?
Tanaka (208 − 0.7×age) tracks measured maxima better than the classic 220 − age, especially over 40. Both carry roughly ±10–12 bpm error — treat the output as a starting band, then adjust with a field test or how effort actually feels.
What is zone 2 and why is everyone talking about it?
Zone 2 is the intensity where you can hold a conversation with slightly longer breaths — roughly 60–70% of max heart rate. It builds aerobic base with low stress and is where most weekly endurance volume is best spent.
Do beta-blockers change heart rate zones?
They lower both resting and maximum heart rate substantially, so percentage-of-max formulas computed from age alone will mislead. Anyone on such medication should set zones with their doctor or use perceived-exertion scales instead.
Is a higher resting heart rate bad?
For adults, 60–100 bpm is the usual reference band, with well-trained people often in the 40s–50s. A sudden sustained rise from your own normal can signal illness, overtraining or dehydration — it is a trend worth watching, not a single reading.
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