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Find your FTP without a test: from real rides

You do not need a 20-minute test to know your FTP – provided you went properly hard at least once in the last few weeks. Here is how to derive a reliable estimate from real rides, and when a test still makes sense.

Updated: October 6, 2026 · 6 min read

What FTP is

Functional Threshold Power (FTP) is the highest power you can hold for roughly one hour. Almost everything in power-based training refers to it: your training zones, the intensity of every session and the load figure TSS. One hour exactly at FTP equals 100 TSS by definition.

If your FTP is set too high, every session looks too easy on paper and you overtrain. If it is too low, your intervals run too gentle and load is underestimated.

Why tests are a hassle

A true one-hour test is so hard that hardly anyone rides it voluntarily. So there are shortcuts: in the 20-minute test you take 95 % of your average power, in Zwift's ramp test 75 % of your best minute. Both work, but they need a fresh day, good pacing and full motivation. Misjudge it and you get a wrong number.

The test-free way: best efforts from real rides

Your rides already contain the information if you went properly hard now and then. Here is how:

1. Collect best efforts. Find your highest 20-minute average power from the last six to eight weeks. That is one point on your power curve.
2. Convert. Multiply by 0.95. Example: a best of 262 W for 20 minutes gives 262 × 0.95 ≈ 249 W, so about 250 W.
3. Cross-check with 5 minutes. For many riders, FTP is roughly 75 to 85 % of best 5-minute power. If your estimate falls far outside, treat it as a warning, not proof – it may simply be your rider profile.
4. Judge whether the effort was maximal. If you deliberately did not go all out for those 20 minutes, the estimate is too low. A value derived from rides is therefore a lower bound: you cannot have ridden more than you rode.

How to check your FTP is right

• Two times 20 minutes at 95 to 100 % of FTP should be very hard but doable.
• If you cannot finish 20 minutes at 100 %, your FTP is probably too high.
• If threshold sessions always feel easy and your heart rate stays low, it is probably too low.

Re-evaluate your FTP every six to eight weeks, or whenever a new best effort overtakes the current estimate.

Without a power meter: lactate threshold heart rate (LTHR)

If you only have heart-rate data, lactate threshold heart rate (LTHR) is the alternative. Load can be estimated from LTHR as well, just less precisely than from power.

Exact test protocol: After warming up, ride alone as hard and steady as possible for 30 minutes. Your average heart rate over the last 20 minutes is your LTHR — not that of the full 30 minutes, because heart rate lags at the start.

From the FTP test (practical): The average heart rate during your 20-minute FTP test is a usable approximation, usually a few beats too high.

Estimate from your data: ZonePit takes the average heart rate during your best 20-minute power effort of the last 90 days. It is only as good as the hardest session in that period.

Keep reading

Sources

• Hunter Allen, Andrew Coggan: Training and Racing with a Power Meter (threshold power, 20-minute test with factor 0.95).
• Zwift: description of the ramp test (FTP = 75 % of best minute).
• Joe Friel: The Cyclist's Training Bible (threshold heart rate, 30-minute test).

ZonePit is a training and wellness app, not a medical device.