Cycling FTP Calculator
Estimate your functional threshold power (FTP) from the average power of an all-out 20-minute ride. Enter your test power in watts and get your FTP plus a suggested training value.
Estimate Your FTP from a 20-Minute Test
Cycling FTP Formula
Where:
- \(P_{20}\) — average power sustained during an all-out 20-minute effort, in watts (W)
- \(\text{FTP}\) — estimated functional threshold power, in watts (W)
This is the widely used method from Hunter Allen and Andrew Coggan's Training and Racing with a Power Meter: multiplying 20-minute average power by 95% approximates the power a rider could hold for a full hour, which is the definition of FTP.
Cycling FTP – Calculation Example
{example}
Example: a rider completes an all-out 20-minute test on the indoor trainer and the head unit reports an average power of 260 W.
\[ \text{FTP} = 0.95 \times 260 = 247 \text{ W} \]
Result: estimated FTP is 247 W, which rounds to a suggested training value of 245 W (nearest 5 W).
{/example}
How to Use the Calculator
- Complete a properly paced 20-minute time-trial effort — ideally after a thorough warm-up and a short hard effort beforehand to pre-fatigue the anaerobic system.
- Check the average power figure on your bike computer or training app for the full 20-minute interval.
- Enter that value in the Average power, 20-minute test field (any value between 50 and 1000 W).
- Read your Estimated functional threshold power (FTP) in watts, along with a Suggested training value rounded to the nearest 5 W, which is what most training platforms expect you to enter.
What Is FTP and Why It Matters
Functional threshold power (FTP) is the highest power a cyclist can sustain for approximately one hour in a quasi-steady state without fatiguing. It is the single most useful number in power-based training because nearly every workout intensity is defined relative to it: recovery rides, endurance rides, tempo, threshold work and VO2max intervals all sit at fixed percentages of FTP.
A direct one-hour time trial is the most accurate way to measure FTP, but it is brutally hard and impractical to do regularly. The 20-minute test with the 95% correction is a well-established compromise: it is demanding but repeatable, and research and coaching practice have shown the adjustment gives a good approximation for most trained riders.
Knowing your FTP lets you set accurate training zones rather than training blind. If your zones are set too low, you undertrain; if too high, you accumulate fatigue and overreach. Retesting every 6–8 weeks during a rested week tracks your progress and keeps workout targets honest. Once you have your FTP, you can use our Cycling Power Zones calculator to generate the exact wattage ranges for each zone.
FTP also gives practical numbers for pacing events: a 40 km time trial is ridden at roughly 100–105% of FTP, a century at around 65–75%, and a short climb well above it. Many riders also track FTP per kilogram of body weight to compare climbing ability across riders.
Limitations and Practical Tips
- The 95% factor is an average, not a law. Sprinters with large anaerobic capacity may overestimate their true one-hour power, while pure time trialists may underestimate it. Treat the result as a starting point, then adjust if workouts in the threshold zone feel consistently too easy or too hard.
- Pacing matters. Starting too hard and fading, or finishing with too much left in the tank, distorts the result. Aim for the hardest power you can hold evenly across all 20 minutes — a slight negative split in the final minutes is ideal.
- Warm up properly. A good warm-up including a few hard efforts makes the 20-minute figure more representative; testing cold usually produces a lower number.
- Keep conditions comparable. Retest on the same course or trainer, at a similar time of day and state of freshness, so changes in FTP reflect fitness rather than circumstances.
- Use the rounded value. Training platforms such as Zwift, TrainerRoad and Sufferfest ask for a whole number, and rounding to the nearest 5 W keeps your zones stable between tests.
- FTP is not the whole picture. Recovery ability, sprint power, and aerobic efficiency all matter for performance. Pairing FTP with markers like heart rate recovery gives a fuller view of your conditioning, and tracking your sweat rate helps you plan hydration for long threshold sessions.
Frequently Asked Questions
How do I calculate FTP by hand without the calculator?
Multiply your 20-minute average power by 0.95. For example, if you averaged 300 W, your FTP is \( 0.95 \times 300 = 285 \text{ W} \). To round to the nearest 5 W manually, divide by 5, round to the nearest whole number, and multiply by 5 again — 285 is already a multiple of 5, so it stays 285 W.
What is a good FTP for my weight or fitness level?
FTP is usually compared per kilogram of body weight. Recreational riders typically sit around 2–3 W/kg, fit amateur cyclists around 3–4 W/kg, competitive racers 4–5 W/kg, and professionals exceed 5.5 W/kg. There is no single "good" number — what matters is whether yours improves over time and whether your training zones based on it feel right for your workouts.
Should I use average power or normalized power from my 20-minute test?
Use straight average power for the 20-minute interval — that is what the 95% formula is built on. If your head unit shows a normalized power much higher than your average power, your pacing was uneven (surges and fades), and the resulting FTP estimate will be less reliable. On a well-paced steady effort the two figures should be close.
Can I use a ramp test instead of a 20-minute test to find my FTP?
Yes. On an incremental ramp test, a common estimate is 75% of the highest power you sustained for a full minute (or your last completed step plus half a step). Ramp tests are easier to pace, but they measure a slightly different ability and often give different numbers than a 20-minute test. Whichever method you choose, stick with it across retests so your numbers are comparable.
Why is my indoor FTP lower than my outdoor FTP?
Indoor rides typically produce 5–10% lower power because of heat buildup, limited cooling, trainer flywheel feel and reduced motivation. This is normal, not a loss of fitness. Test in the same conditions every time — if you set your FTP indoors, use it for indoor training, and consider a separate outdoor test if you mostly ride outside.
What is the most common mistake when doing a 20-minute FTP test?
Including warm-up or cooldown power in the average. Use the lap function on your bike computer so the average covers only the 20-minute effort itself. The other frequent error is bad pacing: going out too hard and fading badly, or coasting at the end. Both distort the average and make the 95% correction inaccurate.
What does it mean if my FTP goes down between tests?
A drop usually means you tested while fatigued, under-slept, or in different conditions — not that your fitness vanished. Retest during a rested, low-volume week. If the number still falls across several tests, review your training load, nutrition and recovery, or consult a coach. For health decisions, always speak with a qualified professional.