What is FTP in Cycling? A Plain-Language Guide

If you've spent any time looking at your cycling data, you've seen the letters FTP. They show up in TrainingPeaks, Intervals.icu, your bike computer, every coaching app. But almost nobody explains what FTP actually is in plain language — or why it's the one number worth understanding before any other.

This guide fixes that.

FTP, in one sentence

FTP (Functional Threshold Power) is the highest average power, in watts, you can sustain for about an hour.

That's it. If your FTP is 250 watts, you could — on a good day, fully motivated — hold roughly 250 watts for an hour before your legs give out. Ride harder than that and fatigue builds fast; ride easier and you can go much longer.

It's "functional" because you don't actually need to suffer for a full hour to estimate it (more on that below), and "threshold" because it sits right at the edge between sustainable and not sustainable effort.

Why FTP matters more than any other number

Here's the part most beginners miss: FTP is the anchor that makes every other training number meaningful.

• Your training zones are calculated as percentages of FTP. Zone 2 endurance, sweet spot, threshold, VO2 max — all defined relative to your FTP.
• Your TSS (training stress) per ride is computed from how your power compared to FTP.
• Your fitness trend (CTL/ATL/TSB) is built on top of that TSS.

Get FTP wrong and every zone, every stress score, and every "am I improving?" answer is wrong too. Get it right and suddenly your whole training picture clicks into place.

How to find your FTP

You have three realistic options, from least to most accurate:

1. Let your data estimate it. Platforms like Intervals.icu detect your FTP automatically from your hardest recent efforts. Good enough to start.
2. The 20-minute test. Warm up, then ride as hard as you can sustainably for 20 minutes. Take your average power for those 20 minutes and multiply by 0.95. That's your estimated FTP.
3. The ramp test. Increasing power every minute until you can't continue. Apps calculate FTP from where you stop. Less painful than the 20-minute test, which is why many beginners prefer it.

Don't obsess over the "perfect" test. A rough FTP you actually train with beats a perfect FTP you never measured.

What to do once you know it

This is where most people stall — they get a number and then... nothing. Knowing your FTP only pays off when it drives structured training: doing the right efforts, in the right zones, on the right days.

That's exactly the gap PlanWatts closes. Connect your data, and it reads your FTP and fitness state, then builds the actual workouts — in your zones — and schedules them around your week. You don't need to memorize zone percentages or design intervals. You get told what to do tomorrow.

The one thing to remember

FTP isn't a trophy — it's a reference point. It will go up as you train and drift down when you rest. Re-test every 4–6 weeks, let your zones update, and let the number do its real job: turning a pile of ride data into a plan that actually makes you faster.