FTP 20 Minute Test Calculator

The 20-minute test is the standard field method for estimating FTP without riding a full hour at threshold. Ride 20 minutes as hard as you can sustain, take the average power, and cut 5%. Enter that average:

The protocol

1. Warm up 15 to 20 minutes, including two or three short accelerations to open the legs.
2. Ride 20 minutes at the hardest pace you can hold to the end — an individual time trial effort, not an opening surge you pay for at minute twelve.
3. Record the average power for the 20 minutes, not the peak.
4. FTP = 95% of that average.

A rider averaging 210 W has an estimated FTP of 210 × 0.95 = 199.5 W. Pacing is the part people get wrong: a test that starts too hard produces a lower average and therefore a lower FTP than the rider actually has, and every zone built on it lands too easy for the next eight weeks.

Why 5% and not something else

FTP is defined as roughly hour-long power, and 20 minutes is a third of that. Almost everyone can push harder for 20 minutes than they could hold for 60, so the raw test number has to be discounted. Five percent is the figure Allen and Coggan proposed, and it is the one used in the peer-reviewed studies that adopt the protocol.

It is worth knowing that the correction is generous. A 2022 review of power profiling points out that 95% of 20-minute power overestimates true 60-minute power, and goes as far as suggesting riders use the raw 20-minute figure for prescribing training rather than converting it at all. The practical consequence: if threshold intervals prescribed from your FTP feel harder than they should, the test, not you, is probably the reason.

Reading the result: watts per kilogram

Raw watts say very little on their own — a 90 kg rider and a 60 kg rider with the same FTP are in different worlds on a climb. Divide by body mass first. Reference points reported in the literature for FTP in watts per kilogram:

Level	FTP (W/kg)
Untrained	around 2
Moderately trained	around 3.3
Well-trained club cyclist	3.5 to 4.5
Male world class	around 6

Those figures come from a study of moderately trained cyclists whose own group averaged 3.3 W/kg. The same study found that relative FTP correlated strongly with finishing time in a 47 km mass-start mountain bike race (r = −0.74), while laboratory VO2 max did not correlate significantly at all — which is the practical case for testing FTP in the first place. The watts per kilogram calculator does the division for you.

After the test

Feed the result into the FTP training zones calculator to get your seven zones in watts. If 20 continuous minutes at the limit is not workable for you, the 8-minute version trades some precision for a shorter effort.