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Enter your FTP and threshold heart rate to get your power and heart-rate training zones instantly. No sign-up, no email — just your numbers.
| Zone | % FTP | Watts |
|---|---|---|
| Z1 · Active Recovery Easy spinning, between-interval and recovery rides | ≤ 55% | — |
| Z2 · Endurance All-day aerobic base; the bulk of most weeks | 56–75% | — |
| Z3 · Tempo Sustained "comfortably hard" efforts | 76–90% | — |
| Z4 · Lactate Threshold Threshold / FTP intervals — the engine of fitness | 91–105% | — |
| Z5 · VO₂ Max 3–8 min hard intervals that raise your ceiling | 106–120% | — |
| Z6 · Anaerobic Capacity 30s–3 min very hard efforts | 121–150% | — |
| Z7 · Neuromuscular Maximal sprints — short and explosive | > 150% | — |
| Zone | % LTHR | BPM |
|---|---|---|
| Z1 · Recovery Active recovery, very easy | < 81% | — |
| Z2 · Aerobic Endurance base pace | 81–89% | — |
| Z3 · Tempo Steady, moderately hard | 90–93% | — |
| Z4 · Sub-Threshold Just under threshold | 94–99% | — |
| Z5a · Super-Threshold At/just over threshold | 100–102% | — |
| Z5b · Aerobic Capacity VO₂-style hard efforts | 103–106% | — |
| Z5c · Anaerobic Maximal, short | > 106% | — |
The next step
The hard part is turning them into a week that fits your life — and rebuilding it when life gets in the way. Joules is a cycling coach you add to Claude or ChatGPT: it holds your zones, your goal event, and your training load, then plans each week around them and adapts when you miss a day. You already pay for the AI — give it a coach's brain.
Power zones are set as percentages of your FTP (functional threshold power) using the classic seven-zone model from Dr. Andrew Coggan. They run from active recovery up through neuromuscular sprints, and they're the most precise way to prescribe intensity because power is instantaneous — it doesn't lag or drift.
Heart-rate zones are set as percentages of your LTHR (lactate threshold heart rate) using Joe Friel's cycling-specific zones. Heart rate reflects how your body is actually responding to a ride, which makes it excellent for endurance pacing — just remember it lags effort by a minute or two and climbs in heat and fatigue.
Want the science behind using these day to day? Read what an AI coach actually needs to know or how to train without a power meter.
Functional Threshold Power (FTP) is the highest average power, in watts, you can hold for roughly an hour. It anchors every power zone. Most riders estimate it from a 20-minute test (take 95% of your 20-min average) or a ramp test.
Lactate Threshold Heart Rate is your average heart rate during a hard, sustained ~30–60 minute effort. Joe Friel's method: do a 30-minute time trial alone, and use your average heart rate over the final 20 minutes as your LTHR.
Power is instant and precise, so it's best for intervals. Heart rate reflects how your body is actually responding and is great for endurance pacing — but it lags effort and drifts with heat and fatigue. Many riders use both: power to set the effort, heart rate to sanity-check it.
Every 4–8 weeks during a training block, or whenever workouts that used to be hard start feeling easy. Fitness moves, and stale zones make every prescription a little bit wrong.
These zones are estimates for training guidance and general fitness, not medical advice. Consult a doctor before starting a new training program. Calculations happen entirely in your browser — nothing you type is sent anywhere.