[CALCULATOR]
FTP from a real effort, and the seven bands under it.
[WHAT THIS DOES]
Functional threshold power is the highest power you could hold for roughly an hour. This estimates it from a sustained effort of at least twenty minutes — scaling by how long the effort already lasted rather than applying a flat 95% to everything — and prints the standard Coggan bands underneath.
What FTP is, and what the number is doing
Functional threshold power is the highest power you can sustain for roughly an hour. It is the cycling analogue of threshold pace, and it does the same job: every training band is a fraction of it, so getting it wrong shifts every session you do.
Power has one enormous advantage over pace for a hybrid athlete. It is immune to terrain, wind, heat and fatigue. 250 watts is 250 watts uphill into a headwind at the end of a long ride. Pace is not — which is why running zones need a heart-rate cross-check on easy days and cycling zones do not.
Why not just take 95% of your 20-minute power
Because that rule was written for a 20-minute test specifically, and people apply it to everything. A 40-minute effort is much closer to FTP than a 20-minute one; discounting it by 5% underestimates you.
This calculator scales the discount with duration: 95% at twenty minutes, rising linearly to 100% at fifty minutes and staying there. That is a smoother version of what every serious protocol does and it means a hard 45-minute climb is usable data rather than a number you have to throw away.
The Coggan zones
| Zone | % of FTP | Typical use |
|---|---|---|
| Z1 Active recovery | under 55% | Spinning between hard days |
| Z2 Endurance | 56–75% | The bulk of weekly volume |
| Z3 Tempo | 76–87% | Sustained sub-threshold work |
| Z4 Threshold | 88–105% | 8–30 minute reps at or near FTP |
| Z5 VO2 max | 106–120% | 3–8 minute reps |
| Z6 Anaerobic | 121–150% | 30s–3min |
| Z7 Neuromuscular | 150%+ | Sprints |
Base prescribes in five session types rather than seven zones, because a session type is a decision and a zone is a measurement: easy 0.55–0.75, long 0.60–0.75, tempo 0.76–0.87, threshold 0.95–1.05, intervals 1.06–1.20.
Cycling is the endurance modality that interferes least
This is the single most useful fact in hybrid programming, and it is not folklore. The concurrent-training meta-analyses find that running produces measurable interference with lower-body strength and hypertrophy and cycling does not, at statistical significance. The mechanistic explanation usually offered is eccentric loading: running is thousands of eccentric contractions per session and cycling is almost none, so running adds muscle damage that has to be repaired out of the same budget your squats are drawing on.
If your endurance goal is sport-agnostic — general conditioning, work capacity, health — biasing toward the bike is close to a free lunch. If your goal is a running race, it is not an option, and the answer is separating sessions by six hours or more instead.
What to do next
Test properly once, then stop testing and start training. Re-estimate every four to six weeks, or when threshold sessions start grading systematically wrong.
Questions
What is a good FTP?
The useful figure is watts per kilogram, not raw watts. Roughly: 2.5 W/kg is a recreational cyclist, 3.5 is a strong club rider, 4.5 is competitive amateur racing, and above 5.5 is the domain of professionals. A hybrid athlete carrying 15 lb more muscle than a pure cyclist will have a worse W/kg at the same fitness, which is the trade being made on purpose.
Does cycling interfere with building muscle?
Much less than running does. Concurrent-training meta-analyses find running produces measurable interference with lower-body strength and size while cycling does not at statistical significance. The usual explanation is eccentric loading: running is thousands of eccentric contractions per session, cycling is almost none, so running adds muscle damage that competes with the repair your lifting needs.
How often should I retest FTP?
Every four to six weeks during a build. More often than that and you are spending training days on testing; less often and you spend weeks training in bands built on a fitness level you have outgrown.
Can I estimate FTP without a power meter?
Not reliably. Heart rate is too lagged and too sensitive to heat, sleep and caffeine; speed is too dependent on terrain and wind. A smart trainer or a power meter is the entry fee for cycling zones, which is precisely the reason running zones in Base are built on pace instead.