FTP Calculator

Your Functional Threshold Power is about 95% of the average power you hold in an all-out 20-minute effort. Enter that number and your weight to get FTP in watts and, more usefully, watts per kilogram.

How the math works

FTP is the highest power you can hold in a quasi-steady state for about an hour, in watts. Testing for a full hour is punishing and rarely done, so the standard field test is a 20-minute maximal effort, then a 5% cut to approximate the hour. The concept and the 0.95 factor come from Allen & Coggan (Training and Racing with a Power Meter, 2019).

The 5% haircut exists because most riders can hold more power for 20 minutes than for 60, thanks to an anaerobic contribution that fades over the longer effort. The factor was set on trained cyclists, so it fits that population best; the 60-minute test remains the reference the 20-minute estimate is standing in for.

Worked example

A cyclist finishes a 20-minute maximal test averaging 280 watts and weighs 165 lb (74.84 kg).

• FTP: 0.95 × 280 = 266 W
• Power-to-weight: 266 ÷ 74.8427 = 3.55 W/kg — the trained / club-racer band
• Why the watts alone mislead: the same 266 W at 190 lb (86.2 kg) is 3.09 W/kg, a full band lower on any climb

When this calculator is wrong

The 0.95 factor lands close on average but has a wide individual band. Borszcz et al. (2018) tested 23 trained men and found the mean difference between 95%-of-20-minute power and a measured 60-minute power was only −1 to −5 W, with strong correlations (r = 0.61–0.88) — but the individual limits of agreement ran up to −62 to +60 W. The 5% cut is a population average, not your number. A rider with a big anaerobic tank — a sprinter or pursuiter who can hold well above threshold for 20 minutes — sits at the high end, so 0.95 × 20-min prints an FTP they can't actually hold for an hour. The exception: a steady, diesel-type rider whose 20-minute power is already close to their 60-minute power will find 0.95 about right, and for tracking your own fitness at a fixed protocol the factor stays constant, so the trend is honest even when the absolute number is a few watts off.

• Pacing wrecks the test. Go out too hard and you fade; the 20-minute average — and therefore the FTP — comes in low. The test only works as a genuinely even, maximal 20 minutes, which usually takes a practice run to pace.
• Power meters disagree. A smart trainer, a crank meter, and a pedal meter can read several percent apart, and that offset carries straight into FTP. Retest on the same device you train with, or your zones will be built on a different scale than your workouts.
• Weight changes move W/kg without moving FTP. Because W/kg divides by bodyweight, a few kilograms shifts your climbing number even if your watts are flat — recompute the ratio when your weight changes, not just when your power does.

What to do with the result

Use FTP as the anchor for training zones and interval targets, then verify it in the real world. Set your power zones as percentages of FTP, program threshold and sweet-spot work off it, and re-test every 4–6 weeks — FTP moves with fitness, and a stale number makes every zone wrong at once. Before you trust a fresh estimate for hour-long threshold work, check it against a real sustained effort: if you can't hold the new FTP for 20–30 steady minutes on a hard day, the 20-minute test flattered you and the true number is lower. Read watts and W/kg for different jobs — raw watts (and aerodynamics) decide flat time trials, while W/kg decides how you climb, so a 266 W rider at 3.55 W/kg is a stronger climber than a heavier 266 W rider at 3.09 W/kg even though the watts match.

Common questions

How do I do a 20-minute FTP test?

Warm up thoroughly (15–20 minutes with a few short openers), then ride as hard as you can hold evenly for 20 minutes on a flat road or a trainer, recording average power. Some protocols add a 5-minute all-out effort before the 20 minutes to pre-fatigue the anaerobic system; either way, the number you feed this calculator is the 20-minute average, and it's ×0.95 to get FTP.

Why multiply by 0.95?

FTP is defined at roughly 60 minutes, and most riders can hold more power for 20 minutes than for a full hour because of an anaerobic contribution that fades over the longer effort. The 5% cut approximates that gap. It's Allen & Coggan's factor, and Borszcz et al. (2018) confirmed it tracks measured 60-minute power on average — with a wide individual spread.

Is a ramp test just as accurate?

A ramp test is easier to pace and popular on indoor platforms, but the common "FTP = 75% of your best 1-minute ramp power" figure traces to platform convention rather than a primary publication, so we don't print a ramp multiplier here. The 20-minute 0.95 rule is the version with a citable source and a peer-reviewed validation behind it.

What's a good FTP in watts?

Watts alone don't answer that — a 266 W FTP is a strong club rider at 60 kg and a recreational number at 100 kg. Use W/kg. On the men's power-profile bands, recreational riders sit around 2.5–3.5 W/kg, trained club racers around 3.5–4.5, and Grand Tour climbers above 6.0 (women's bands run lower). The bands are approximate context, not a grade.

How often should I retest?

Every 4–6 weeks during a training block, or after any change big enough to move fitness — a training camp, a break, a bout of illness. Testing more often than that mostly measures test-day noise (sleep, heat, motivation) rather than a real change in threshold.

Does FTP change indoors versus outdoors?

Often, yes — many riders record a lower FTP on a trainer than on the road, from heat, a fixed position, and less motivation. It's also partly a power-meter offset. Test and train on the same setup so your zones match the workouts you'll actually do in that environment.