If you only ever track one number in cycling, make it this one. FTP — functional threshold power — is the single most useful figure in training, because almost everything else is built on top of it. Your training zones, your interval targets, your sense of whether you’re getting fitter or just getting tired — all of it anchors to FTP. Here’s exactly what it is and how to find yours, without a lab and without overthinking it.

What FTP actually is

FTP is the highest average power, in watts, that you can hold for roughly an hour. That’s it. It’s a practical stand-in for your physiological threshold — the intensity where fatigue starts to climb sharply — and it splits “hard but sustainable” from “burning matches you won’t get back.”

Why an hour? Because that’s long enough that you can’t fake it with anaerobic effort, and short enough to reflect the kind of sustained power that actually wins (or survives) real rides. A rider with an FTP of 280 W isn’t guessing about their next climb — they know what they can hold and for how long.

Why FTP is the number everything hangs off

FTP matters because it sets your training zones. Endurance, tempo, sweet spot, threshold, VO2 max — every zone is a percentage of FTP. Get FTP right and your zones are right, which means your easy days are genuinely easy and your hard days actually hit the system you’re trying to develop. Get it wrong and you spend weeks training the wrong intensity, wondering why you’re not improving.

It’s also the cleanest single marker of fitness over time. Watch your FTP across a season and you can see your base build, your peak arrive, and your form fade if you’ve overcooked it. Power-to-weight (FTP ÷ kg) is what people quote when they compare climbers — but the raw number is where it starts.

How to find your FTP (three honest options)

• The 20-minute test. The classic. Warm up properly, then ride as hard as you can hold for 20 minutes, flat out but even. Take your average power and multiply by 0.95. That 5% haircut accounts for the difference between 20 minutes and a true hour. It hurts, but it’s reliable.
• The ramp test. Power steps up every minute until you can’t hold the next step. Software estimates FTP from the peak (usually ~75% of your best 1-minute power). Shorter and less brutal — good if you dread the 20-minute effort.
• Just ride and watch the data. If you train consistently with power, your best 40–60 minute efforts on hard rides quietly reveal your threshold without a dedicated test at all.

Do you need a power meter to know your FTP?

Traditionally, yes — FTP is a power number, and power means a meter. But you don’t have to start there. HELIOS estimates your power from a physics model of your ride — speed, gradient, weight, conditions — so you can track threshold and zones from day one. It’s labelled EST (estimated) and it’s honest about that: phone-and-ring power is excellent for trends and for training to consistent zones, and it gets exact when you pair a meter. The point is you can train properly to FTP now, not “once you’ve bought a power meter.”

How to actually use your FTP

Once you have a number, two things happen. First, set your zones off it — now every workout has a real target instead of “ride sort of hard.” Second, retest every 4–8 weeks, because FTP moves as you do. A rising FTP says the training is working; a stalled or falling one says you need more recovery or a different stimulus.

This is where it stops being a number on a screen and becomes a plan. HELIOS takes your FTP and builds your training around it — the right zones, the right intervals, periodised toward your goal — and Marco, the AI coach, adjusts it as your threshold and recovery change. You find the number once; the system keeps it current.

The mistakes that wreck FTP tests

• Going out too hard. The 20-minute test is paced, not a sprint. Blow up at minute 5 and your number is garbage.
• Testing tired. Test on a fresh day, or you’re measuring your fatigue, not your fitness.
• Never retesting. An FTP from three months ago is training you to the wrong zones today.

The bottom line

FTP is the foundation the rest of your training stands on. Find it with a 20-minute or ramp test (or let consistent power data reveal it), set your zones off it, and retest every month or so. Do that and every ride has a purpose — and the watts follow.