FTP Test Calculator

Frequently Asked Questions

What is FTP?

Functional Threshold Power is the highest average watts you can sustain for ≈1 hour. It anchors training zones, TSS, and IF; small accurate changes (5–10 W) materially shift workout intensity.

How does the 20-minute test estimate FTP?

After a structured warm-up, ride a maximal 20-min effort; FTP ≈ 20-min average power × 0.95. The 5% discount approximates the drop-off from 20 min to 60 min for trained riders.

What about 8-minute or ramp tests?

8-min: FTP ≈ 8-min average power × 0.90 (often two intervals averaged). Ramp test: FTP ≈ best 1-min average power at exhaustion × 0.75. Ramp tests are popular indoors because they're shorter and lower-strain.

Which protocol is most accurate?

A true 60-min time trial is the gold standard but brutal. Trained riders usually find the 20-min test closer than the ramp; newer riders often over-test on ramp (high anaerobic contribution). Re-test every 6–8 weeks using the same protocol.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Functional Threshold Power (FTP) is the highest average power in watts that a cyclist can sustain for approximately one hour. Because a full one-hour all-out effort is brutal and rarely worth the recovery cost, coaches use shorter field tests and apply a correction factor to estimate FTP. Pick the protocol you actually performed, enter the average power for that interval, and the calculator returns your estimated FTP. Optionally add your body weight to convert FTP into watts per kilogram (W/kg) - the metric that actually determines how fast you climb. The three supported protocols are the classic 20-minute test (Allen & Coggan), the 2×8-minute test popularised by Hunter Allen, and the ramp test used by TrainerRoad and Zwift.

Formula / Method

The estimates use three well-published factors. 20-minute test: FTP ≈ AvgPower_20min × 0.95. The 5% haircut accounts for the fact that you can almost always push slightly above true one-hour power for twenty minutes. 8-minute test: FTP ≈ AvgPower_8min × 0.90. With only eight minutes of work, anaerobic contribution is larger, so the discount is bigger. Ramp test: FTP ≈ MaxMinutePower × 0.75 where MaxMinutePower (MMP) is the average wattage of the final completed minute before failure. The ramp typically starts at roughly 50% of estimated FTP and increases by ~6% every minute. Of the three, the ramp is the least painful but also the most dependent on anaerobic capacity, so riders with strong sprints may see slightly inflated numbers.

Worked Example

Suppose you complete a 20-minute test and your power meter reports an average of 280 watts. Estimated FTP = 280 × 0.95 = 266 W. If you weigh 72 kg, your power-to-weight ratio is 266 ÷ 72 ≈ 3.69 W/kg, putting you in the upper-Cat 4 / lower-Cat 3 range for amateur road racing. If instead you finished the ramp test with a final minute averaging 350 W, estimated FTP = 350 × 0.75 = 263 W. The two protocols agree within a few watts - a good consistency check when you switch testing methods.

Common Mistakes

Skipping the warm-up. The 20-minute test in particular demands a 15–20 minute warm-up with several short openers above threshold or your first 5 minutes will be artificially low.

Pacing the 20-minute test like a sprint. The classic pattern is to start at FTP + 5% and only push above in the final 3 minutes - not blow up at minute 8.

Mixing trainer and outdoor numbers. Indoor power is typically 5–10% lower for the same perceived effort, so always retest on the same surface.

Reading FTP as fixed for a season. FTP shifts with training load, heat, altitude, and fatigue - retest every 4–8 weeks.

Ignoring the calibration. A trainer that hasn't had a spin-down in months can read 10–15 W off and silently corrupt every workout zone.

Tips & FAQ

Which test should I pick? Beginners: ramp test - lowest psychological barrier. Intermediate riders preparing for races: 20-minute test - the gold standard. Riders with strong anaerobic systems (track sprinters, crit specialists): 2×8-minute test, which dampens their advantage. How do training zones flow from FTP? Coggan's seven-zone model anchors everything to %FTP: Z1 active recovery < 55%, Z2 endurance 56–75%, Z3 tempo 76–90%, Z4 threshold 91–105%, Z5 VO2 max 106–120%, Z6 anaerobic 121–150%, Z7 neuromuscular > 150%. Can I just guess from a long climb? Yes - a 20-minute all-out climb works fine as a 20-minute test, often producing a slightly higher number because the steady gradient and cooler air help. Is W/kg or absolute watts more important? W/kg dominates climbing; absolute watts dominate flat sprints and time trials. Track both.

Frequently Asked Questions

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