Zone 2 heart rate is usually defined as 60–70% of max heart rate, 60–70% of heart-rate reserve (the Karvonen method), or 85–89% of lactate threshold heart rate (Joe Friel’s running zones). For a 35-year-old runner with a max HR of 185, resting HR of 55 and LTHR of 168, those three rules give 112–130 bpm, 134–146 bpm and 144–150 bpm. The ranges barely overlap, and that is why your watch, your training app and your coach can each give you a different zone 2.
None of them is a typo. Each formula starts from a different anchor and uses a different definition of “zone 2”. Below are the numbers for two example athletes, the reasons they differ, and how to pick one method and stick with it.
The five ways to calculate zone 2
1. Percentage of max heart rate
Zone 2 = 60–70% of max HR. You only need one number, which is why many watches use it by default. The weakness is that it ignores resting heart rate and fitness, and it gives the lowest zone 2 of the methods compared here.
2. Heart-rate reserve (Karvonen)
Heart-rate reserve (HRR) is max HR minus resting HR. Karvonen’s 1957 training study (Karvonen et al., 1957) is the origin of this approach. The percentage is applied to the reserve and resting HR is added back:
Zone 2 = resting HR + (0.60 to 0.70) × (max HR − resting HR)
A fitter athlete with a low resting HR gets a wider reserve. Because resting HR is added back on top, Karvonen zones always come out higher than the same percentages of max HR.
3. Percentage of lactate threshold heart rate (Friel)
Friel anchors zones to LTHR, which he estimates from a solo 30-minute running time trial: the average HR over the last 20 minutes of that effort. His running zone 2 is 85–89% of LTHR (Friel, TrainingPeaks). His cycling zone 2 is wider (81–89%), so runners and cyclists should not share one table. Friel also says plainly not to use 220 minus age, because it “is as likely to be wrong as right.”
4. MAF 180 formula (Maffetone)
Take 180 minus your age, then adjust by −10, −5, 0 or +5 depending on health, training history and recent progress (Maffetone, MAF 180 Formula). The result is a ceiling, the “maximum aerobic heart rate”, not a range. Maffetone himself writes that 180 minus age “is not associated with VO2max, lactate threshold, or other traditional measurements.” Treat it as a practical cap, not a physiological measurement.
5. Talk test and ventilatory threshold
You need no formula for this one. Zone 2 is the effort where you can still speak in full sentences comfortably. In a lab study by Persinger et al. (2004), the point where speech first became difficult lined up closely with the ventilatory threshold on both a treadmill and a bike, and intensities where talking was uncomfortable were consistently above it. Zone 2 sits just below that point. Once you’ve found it, read the heart rate off your monitor and you have a zone 2 measured on your own body.
Zone 2 compared for two example athletes
Computed with the Endurance Toolbox HR Zone Calculator (% max HR, Karvonen and Friel LTHR methods). The MAF value is plain 180 − age arithmetic before Maffetone’s adjustments.
- Athlete A: 35 years old, measured max HR 185, resting HR 55, LTHR 168
- Athlete B: 55 years old, measured max HR 172, resting HR 50, LTHR 155
| Method | Formula | Athlete A (35) | Athlete B (55) |
|---|---|---|---|
| % max HR | 60–70% of max | 112–130 bpm | 104–120 bpm |
| Karvonen (HRR) | 60–70% of reserve + resting | 134–146 bpm | 124–135 bpm |
| Friel % LTHR (run) | 85–89% of LTHR | 144–150 bpm | 133–138 bpm |
| MAF 180 | ceiling, 180 − age | ≤145 bpm (135–150 after adjustment) | ≤125 bpm (115–130 after adjustment) |
| Talk test | full sentences, just below VT1 | measured, not calculated | measured, not calculated |
For Athlete A, the top of zone 2 moves from 130 to 150 bpm depending on which row you trust. That 20-beat gap is the whole reason people argue about zone 2.
Worked example 1: Athlete A, age 35
- % max HR: 0.60 × 185 = 111, so the zone starts at 112; 0.70 × 185 = 129.5, which rounds to 130. Zone 2 = 112–130 bpm.
- Karvonen: reserve = 185 − 55 = 130. 55 + 0.60 × 130 = 133, so the zone starts at 134; 55 + 0.70 × 130 = 146. Zone 2 = 134–146 bpm.
- Friel: 0.85 × 168 = 142.8 and 0.89 × 168 = 149.5. The calculator rounds these to whole-beat zone edges: 144–150 bpm.
- MAF: 180 − 35 = 145 bpm ceiling. If she has trained consistently for more than two years without injury and is still improving, Maffetone’s +5 makes it 150.
Converted to a common scale, Friel’s zone 2 for this runner is 78–81% of max HR. The %-max method calls that zone 3, edging into zone 4.
If Athlete A covers 6.5 km in her 30-minute test, the 30-Minute Run Threshold Calculator puts her threshold pace at 4:37/km (7:26/mi) and Friel’s pace zone 2 at 5:16–5:57/km (8:29–9:35/mi). Use that as a check: if her heart rate on an easy run at 5:40/km drifts well above 150, something other than fitness (heat, fatigue, a bad strap reading) is pushing it up.
Worked example 2: Athlete B, age 55
- % max HR: 104–120 bpm
- Karvonen: reserve = 172 − 50 = 122. Zone 2 = 124–135 bpm
- Friel: 133–138 bpm from an LTHR of 155
- MAF: 180 − 55 = 125 bpm ceiling
Here the MAF ceiling (125) sits at the very bottom of the Karvonen zone 2 (124–135), and Friel’s zone 2 starts above the MAF cap. If Athlete B follows MAF, nearly all his easy running will fall in what Friel calls zone 1. That isn’t wrong. It’s a more conservative philosophy.
Why zone 2 by age is the least reliable approach
Typing your age into a calculator means max HR is guessed, and every downstream number inherits the guess. The classic 220 − age equation was re-examined by Tanaka et al. (2001). Using data from 351 studies and 18,712 subjects, they proposed 208 − 0.7 × age and found that 220 − age underestimates max HR in older adults. Both are regression lines through group averages. Neither tells you where you sit relative to the line.
Here is the same calculator output when only the max-HR input changes:
| Max HR input | Athlete A % max zone 2 | Athlete A Karvonen zone 2 |
|---|---|---|
| 175 (measured − 10) | 106–122 bpm | 128–139 bpm |
| 185 (measured; also 220 − 35) | 112–130 bpm | 134–146 bpm |
| 184 (Tanaka, 183.5 rounded) | 111–129 bpm | 133–145 bpm |
| 195 (measured + 10) | 118–137 bpm | 140–153 bpm |
For Athlete B, 220 − 55 = 165 and Tanaka gives 169.5, both below his measured 172. With 165 entered, his %-max zone 2 drops to 100–115 bpm and his Karvonen zone 2 to 120–131 bpm. An age formula that misses your max HR by 10 beats shifts your whole zone 2 by 6–8 beats.
Why apps and coaches disagree about “zone 2”
1. Different anchors. Max HR, heart-rate reserve and LTHR are different quantities. LTHR sat at about 90–91% of max for both example athletes, but that ratio varies from person to person, so no fixed conversion between the systems exists.
2. Different numbers of zones. A 5-zone %-max model and Friel’s 7-zone model (1, 2, 3, 4, 5a, 5b, 5c) both have a “zone 2”, but they cut the same intensity range at different points.
3. A different meaning in research. Endurance research often uses a 3-zone model built on two ventilatory or lactate thresholds. In that model “zone 2” means the band between the thresholds, which is harder than the easy running most people mean by zone 2. Seiler (2010) describes elite athletes doing about 80% of sessions at low intensity (around 2 mM blood lactate). The popular “zone 2” falls in that low-intensity band, not in the research model’s zone 2.
4. Lab definitions. Lab work such as San-Millán & Brooks (2018) measures blood lactate and fat oxidation directly, and found the two inversely correlated across pro athletes, moderately active people and people with metabolic syndrome. A lab test can find the highest intensity before lactate starts to rise. A formula can only estimate it.
How to pick a zone 2 method
- You have a recent 30-minute test or race-effort data: use Friel % LTHR. It is anchored to your own threshold, not a population average.
- You know your true max HR (from a hard race finish or a supervised test) and your morning resting HR: use Karvonen.
- You only know your age: use the talk test first, then check it against MAF or Karvonen with a Tanaka-estimated max. Treat any age-based number as provisional.
- You’re returning from illness or injury, or are new to structured training: the MAF ceiling or the talk test errs on the easy side, which suits that situation.
Whichever method you choose, use the same one for months. Zone 2 matters because you can repeat it from week to week. Switching between methods will show changes in heart rate that came from the formula, not from your fitness.
How to get your zone 2 range in the HR Zone Calculator
Open the HR Zone Calculator and set Calculation Method:
- Joe Friel (Lactate Threshold): enter your LTHR in the LTHR field. The “Zone 2: Aerobic” row is your range (144–150 bpm for Athlete A).
- Karvonen (Heart Rate Reserve): enter Max HR and Resting HR. Read “Zone 2: Endurance” (134–146 bpm for Athlete A).
- Simple % of Max HR: enter Max HR only. Read “Zone 2: Light” (112–130 bpm for Athlete A).
If you don’t know your LTHR, do the test first: run 30 minutes as hard as you can sustain, alone, and enter the distance and the Avg HR (Last 20 Minutes) into the 30-Minute Run Threshold Calculator. It returns your LTHR, your Friel heart-rate zones and your pace zones in one table. Its zone edges are computed with slightly different whole-beat rounding (Athlete A’s zone 2 shows as 143–151 bpm there), a 1-beat difference that doesn’t matter in training. If you also want an aerobic-fitness benchmark from the same kind of field test, the VO2 max calculator estimates it from a Cooper or 1.5-mile run, and the VO2 max chart by age shows how that estimate compares with lab-measured values.
Limitations
- Every input is an estimate. A 30-minute LTHR test depends on pacing; Friel notes that most people start too hard and fade, and that results improve with repetition. Resting HR changes with sleep, stress and illness.
- Heart rate lags and drifts. On long runs, in heat or when dehydrated, HR rises at a constant pace (cardiac drift). Staying in zone 2 late in a hot run may mean slowing down a lot.
- Optical wrist sensors can lock onto cadence or lag at the start of a run. A chest strap is more reliable for setting zones.
- Running and cycling differ. LTHR is sport-specific, so test each sport separately. Friel publishes separate bike zones, and the calculator’s LTHR table is the running version.
- Medications and medical conditions. Beta-blockers and some heart conditions change the heart-rate response, so no formula here applies. If you have a cardiac condition or take medication that affects heart rate, get your training intensities from a physician or a clinical exercise test.
- Formulas describe, they don’t diagnose. Only lactate or gas-exchange testing measures the thresholds that zone 2 is meant to sit under. The methods above are field approximations of that measurement.