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Free lactate threshold tool: turn a 20- or 30-minute field test into LTHR (with optional ×0.95), estimate cycling FTP from 20-minute watts, and view %LTHR and %FTP zone tables. Educational—pair with FTP tools and pace math, not a lab substitute.
Last updated: May 25, 2026
Method
20-minute test average × 0.95 (common cycling / mixed field rule)
Estimated LTHR: 162 bpm
| Zone | Name | % LTHR | BPM |
|---|---|---|---|
| Z1 | Recovery | < 85% | < 138 bpm |
| Z2 | Aerobic | 85–89% | 138–144 bpm |
| Z3 | Tempo | 90–94% | 146–152 bpm |
| Z4 | Sub-threshold | 95–99% | 154–160 bpm |
| Z5a | Super-threshold | 100–102% | 162–165 bpm |
| Z5b | Aerobic capacity | 103–106% | 167–172 bpm |
| Z5c | Anaerobic | ≥ 107% | ≥ 173 bpm |
Not medical advice. Heat, fatigue, caffeine, and device error change HR; power needs a calibrated meter. Compare with our target heart rate and FTP calculator for alternate methods.
170 × 0.95 = 162 bpm
LTHR
162
bpm
Z4 sub-threshold
154–160 bpm
95–99% LTHR
Z5a super-threshold
162–165 bpm
100–102% LTHR
The multiplier depends on how you collected the average heart rate—wrong protocol = wrong LTHR.
170 × 0.95 = 162 bpm
Hard steady 20 minutes; enter mean HR. Produces LTHR 162 bpm in the default case.
175 bpm average → LTHR 175 bpm (no multiplier).
Discard first 10 minutes when averaging.
192 × 85% = 163 bpm
→ LTHR 163 bpm. Ballpark only—field test when able.
| Case | LTHR | FTP | Sample zone |
|---|---|---|---|
| Default — 170 bpm, 20 min × 0.95 | 162 | — | 154–160 bpm |
| 30 min test — last 20 min avg 175 bpm | 175 | — | 166–173 bpm |
| % max HR — 192 bpm, 85% | 163 | — | 155–161 bpm |
| Cycling — 280 W, 20 min | — | 266 W | 242–279 W |
| Cycling — 260 W, 20 min | — | 247 W | 225–259 W |
Retest every 6–12 weeks in a build phase, or after a training block, using the same protocol, time of day, and warm-up.
More power durations? Cycling FTP calculator. Marathon pace bands? Marathon training pace zones.
LTHR = 175 bpm. Z3 tempo 158–165 bpm; Z4 166–173 bpm. Use for run intervals—not for bike power sessions.
FTP 266 W. Sweet-spot style work often sits ~88–94% FTP (234–250 W). Threshold intervals ~91–105% FTP → 242–279 W.
260 W × 0.95 = 247 W FTP → 247 W FTP vs 280 W × 0.95 = 266 W FTP → 266 W FTP — about 19 W higher threshold anchor (~8% increase).
Send to training partners setting LTHR or FTP zones
Suggested hashtags: #LactateThreshold #LTHR #FTP #Cycling #Running