You've seen FTP printed on your head unit hundreds of times, but there's a good chance you're still using the number loosely. Understanding what cycling FTP actually represents, and how to measure it properly, is the difference between training on feel and building fitness on purpose.

What cycling FTP actually means

FTP stands for Functional Threshold Power. In plain terms, it's the highest power output you can sustain for roughly one hour when you're fresh. Physiologically, it marks the point where lactate starts accumulating faster than your body can clear it. Ride below it and you can hold the effort for a long time; push above it and the clock starts working against you.

FTP is expressed in watts, and it's often quoted relative to body weight as watts per kilogram (W/kg), which matters enormously when the road tilts up. An FTP of 280 W for a 70 kg rider works out to 4 W/kg, a respectable figure for a committed gran fondo cyclist. But the raw number on its own tells you very little until you know what to do with it.

Why FTP is your training anchor

FTP isn't a bragging-rights stat for the coffee-stop group chat. Its real job is to act as the anchor for your entire training plan. Every intensity target you follow flows from it: your training zones are calculated as percentages of FTP, and your weekly sessions (endurance rides, threshold repeats, over-unders, VO2max intervals) are prescribed against those zones. Without a reliable FTP, every intensity instruction is essentially a guess.

There's a second benefit. Tracking FTP over time tells you whether your training is actually working. If your number climbs after eight weeks of structured work, you have objective confirmation. If it's flat or falling, something needs attention, and more often than not it's recovery rather than load.

How to calculate FTP: the 20-minute test

The most widely used and accessible protocol is the 20-minute test. You'll need a reliable power meter, a stretch of road or a trainer where you can ride hard without interruption, and the willingness to suffer honestly. Here's how it goes:

  • Warm up properly: 15-20 progressive minutes with a few short surges to open the legs.
  • Opening effort: a 5-minute near-maximal blow-out to deplete the anaerobic contribution, followed by a few minutes of easy spinning to recover.
  • The test itself: 20 minutes at the highest steady effort you can hold. Don't go out too hard; blowing up in the first five minutes is the classic mistake.
  • The calculation: take your average power for the 20 minutes and subtract about 5%.

A worked example: if you averaged 300 W across the twenty minutes, your estimated FTP is roughly 285 W (300 minus 5%). That subtraction exists because 20 minutes is shorter than a true hour, so the power you produce is slightly higher than what you could actually hold for a full sixty minutes.

The alternative: the ramp test

If twenty minutes of self-inflicted pain is mentally daunting, there's the ramp test. It's a graded effort: you start at a low power and the target steps up every minute until you can no longer hold the pace. Software then estimates your FTP from the final completed step, typically around 75% of that peak one-minute power.

The ramp test is shorter, less dependent on pacing strategy, and easy to repeat in a standardized way on the trainer. The trade-off is that it rewards riders with a strong anaerobic kick and can overestimate FTP for the diesel-engine types who are highly aerobic but not explosive. Whatever method you pick, consistency is what counts: only ever compare tests run with the same protocol.

Turning your threshold into training zones

Once you have an FTP, you can build your power zones. The most common framework (the Coggan model) splits intensity into seven bands, each defined as a percentage of FTP. Broadly:

  • Active recovery: below 55% of FTP.
  • Endurance: 56-75%, the aerobic base of your long rides.
  • Tempo: 76-90%, the "hard but controlled" pace.
  • Threshold: 91-105%, right around your FTP.
  • VO2max and above: over 106%, the short, sharp intervals.

These percentages turn an abstract number into concrete instructions. When your plan says "3x10 minutes at threshold," you know exactly what wattage to chase rather than relying on perceived effort alone.

Common mistakes, and what matters beyond FTP

Even the best protocol is wasted if you execute it badly. The most frequent errors are: testing with tired legs after a heavy training block, testing far too rarely (an FTP from six months ago no longer describes your current fitness), and switching protocols each time so your numbers can't be compared. Ideally, retest every 4-6 weeks under controlled, repeatable conditions.

There's also a deeper limitation worth internalizing: FTP on its own is an incomplete picture. It measures your threshold power, but it says nothing about your ability to sprint, your durability on a long climb, your resistance to fatigue after four hours in the saddle, or how repeatable your hard efforts are deep into a gran fondo. Two riders with identical FTPs can race in completely different ways. FTP is your starting point, not the full portrait.

This is exactly where a structured method earns its keep. Per Pro is built on the work of World Tour coaches and begins with a two-day assessment that profiles far more than FTP alone: aerobic capacity, threshold, durability, and your power-duration profile. From that real baseline, coaches construct your zones and a plan calibrated to your actual week rather than an idealized one. It's the same method that takes professionals to the start line, rewritten around your real life.

The takeaways

  • FTP is the highest power you can hold for about an hour: the anchor of your training.
  • The 20-minute test is the most accessible: average watts minus 5% (300 W → 285 W).
  • The ramp test is a valid, shorter alternative, with its own biases.
  • Your zones, and therefore every session, are derived from FTP.
  • Don't test fatigued, retest every 4-6 weeks, and keep the protocol identical.
  • FTP matters but is incomplete: sprint, endurance, and durability count too.