Do I need a power meter?

For a true FTP, yes. A smart trainer works too. Without power measurement, threshold heart rate is the only stand-in.

How often should I test?

Every six to twelve weeks is plenty. Testing more often costs more recovery than it yields in insight.

My FTP dropped — did I do something wrong?

Not necessarily. A test also measures daily form. Fatigue, heat or a hard week beforehand push the number down without your fitness being worse.

FTP Calculator

Calculate Functional Threshold Power from a test

Test method

Avg power 20 min (W)

Body weight (kg)

238 W

3.4 W/kg

Training zones

Z1Active recovery

0–131 W

Z2Endurance

133–179 W

Z3Tempo

181–214 W

Z4Threshold

217–250 W

Z5VO2max

252–286 W

Z6Anaerobic

288–∞ W

What FTP means

FTP is the power in watts you can sustain on the bike for roughly an hour. It is the key reference in cycling training — almost everything else derives from it.

Because a full hour at the limit is brutal and hard to schedule, most people test for 20 minutes and subtract a little. The calculator does that for you.

How it is calculated

20-minute test: FTP = average power over 20 minutes × 0.95. Ramp test: FTP = best 1-minute power × 0.75.

Over 20 minutes your anaerobic capacity still contributes noticeably; taking off 5 % brings the number down to what you can hold for about an hour. In a ramp test the final minute sits far above threshold, hence the larger discount.

20-minute example: 280 W average. 280 × 0.95 = 266 W FTP. At 72 kg body weight that is 266 / 72 = 3.7 W/kg.

Ramp example: best minute 350 W. 350 × 0.75 = 263 W FTP.

The zones are percentages of that value: Z2 endurance 56 to 75 %, Z4 threshold 91 to 105 %, Z5 VO2max 106 to 120 %. With an FTP of 266 W the threshold zone is 242 to 279 W.

If you want to calculate FTP without riding the full test, choose the ramp test over a guessed 20-minute number — it is shorter and easier to repeat.

What the value gives you

With FTP you get training ranges in watts instead of by feel. On the bike that is more precise than heart rate, which reacts slowly and shifts with heat and fatigue.

A single value says little. It becomes useful when you retest every few months and watch the direction.

Frequently asked questions

Do I need a power meter?: For a true FTP, yes. A smart trainer works too. Without power measurement, threshold heart rate is the only stand-in.
How often should I test?: Every six to twelve weeks is plenty. Testing more often costs more recovery than it yields in insight.
My FTP dropped — did I do something wrong?: Not necessarily. A test also measures daily form. Fatigue, heat or a hard week beforehand push the number down without your fitness being worse.