FTP calculator

Every common field test is a short effort with a multiplier applied to it, because almost nobody actually rides a full hour flat out to measure FTP directly.

• Ramp test → 75% of the last completed minute. The power steps up every minute until you cannot hold it. Short, brutal, and the easiest to pace because pacing is impossible.
• 20-minute test → 95% of the average. The classic. Needs real pacing discipline: go out too hard in the first three minutes and the number is wrong in both directions.
• 8-minute test → 90% of the average. Usually ridden as two 8-minute efforts; take the better one. Kinder to the schedule, less reliable.

All three are estimates. The ramp test tends to flatter riders with a strong top end and punish diesel engines; the 20-minute test does the opposite. The number that matters is the one you can hold in a real session — which is why rating each session afterwards is worth more than arguing about the test.

Every four to six weeks. More often than that and you are measuring noise — a single bad night's sleep moves a ramp test more than a month of training does. Less often and you spend weeks training at targets that no longer fit.

Test on a day that can take it: after a rest day, not after a run of night shifts, and at the same time of day each time. My own plan puts four tests in sixteen weeks and moves any test that lands on a bad morning — you can see them on the plan.