Zone 2 calculator · Free · 30 seconds
Train in the zone that actually extends life.
Zone 2 builds mitochondrial density, lifts VO2 max, and lowers all-cause mortality more than any other training intensity. Pick a method, get your range, train it 2–3 times a week.
- Three validated methods: Maffetone, HR reserve (Karvonen), and % of LTHR
- Method comparison helps you pick what's most accurate for your fitness level
- Live HR-band visualization with a real-time gradient
- Plain-English explanation of what zone 2 should feel like
- Built-in training prescription (2–3 sessions/week, 45–60 min each)
Why zone 2
+30–40% mitochondrial density
Over 12 weeks of 2–3 sessions/week
5× lower all-cause mortality
Elite vs low VO2 max (Mandsager 2018)
−5 bpm resting HR
Typical adaptation in 8–10 weeks
Zone 2 heart-rate calculator
Three methods — Maffetone, HR reserve, or % of LTHR
Used by Maffetone + max HR estimate
years
Your zone 2 range
132–142bpm
Maffetone MAF (180 minus age)
112132142162
Mechanism: Phil Maffetone's MAF formula gives a single conservative aerobic ceiling. Optimized for fat oxidation + base building over 12+ weeks.
How it should feel: Easy nasal breathing. Conversation comfortable. Slight tightness if you push the top of the range.
⚠ MAF is conservative. Trained athletes will find their LT1 (true zone-2 ceiling) is 5–15 bpm higher.
Target 2–3 sessions per week of 45–60 min in this band for 12 weeks to see VO2 max improvement. Pair with one weekly Norwegian 4×4 session for faster gains.
Frequently asked
Common questions
% of LTHR is the most accurate — but requires a real 30-min time trial to measure your lactate threshold heart rate. If you haven't tested, Karvonen (HR reserve) is the next-best because it accounts for individual fitness (resting HR). Maffetone is the easiest but most conservative — well-trained athletes will find their actual LT1 sits 5–15 bpm above the MAF number.
After a 15-minute warm-up, do an all-out 5-minute effort on a hill or flat track with a heart rate strap (chest strap, not wrist). The peak HR you hit in the last 60 seconds is a reliable proxy for max HR. Repeat once for confidence. Don't use age formulas — they have ±10–12 bpm error per individual.
Mitochondrial density adaptations begin within 4 weeks. Measurable VO2 max improvement typically shows by 8–12 weeks with 2–3 sessions per week of 45–60 minutes each. Resting heart rate often drops 4–8 bpm in the same window. For competitive athletes, a 6-month accumulation produces substantially more durability than the first 12 weeks suggest.
Yes to all three. Pick whichever lets you stay in the band consistently. Bike and rower are easier for new athletes because terrain doesn't push you out of zone. Running on flat ground is fine — hills will inevitably spike you into zone 3, which dilutes the adaptation. The watt zone (cycling power) ≈ 56–75% of FTP, which maps roughly to the HR ranges this calculator produces.
Optional. Fasted zone 2 emphasizes fat oxidation and may marginally improve metabolic flexibility. Fed zone 2 lets you push the upper end of the band for slightly more training stimulus. Both produce the mitochondrial adaptations. Pick what you can sustain. If your sessions are >75 minutes, fed is more comfortable.
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