FTP test with Zwift: How performance and level tests are carried out and analysed
Robert Kühnen
· 18.12.2025
The article first appeared in 2022, was updated in December 2025
Indoor training on smart trainers is controlled by the pedalling power, which is displayed in watts. The power in watts is the linchpin for everything. The possible pedalling power varies according to fitness level, body weight - and, crucially, the length of the workout. In a sprint, a multiple of the continuous power is possible. The measure of endurance performance is usually the FTP power (FTP = Functional Threshold Power). This is the maximum power over one hour.
From the FTP the Training zones which describe the training intensities. The FTP in relation to body weight gives the power rating in watts per kilo (W/kg) for Zwift race. On the mountain in particular - both indoors and outdoors - watts per kilogramme are the currency that determines your pace on the mountain. The FTP provides immediate orientation as to where an athlete stands in the performance pyramid: The spectrum ranges from 1.5 W/kg (untrained) to 6.5 W/kg (absolute world class). Regular testing of the FTP is one way of visualising progress in performance.
As it is very demanding to call up the maximum performance over an hour, the FTP test is usually shortened and the FTP performance is extrapolated from the 20-minute performance.
FTP tests from Zwift
Zwift offers four test protocols relating to FTP, two short step tests and two FTP tests of different lengths.
1. step tests for an initial assessment of the FTP
If you have never taken a test before and don't know where your personal FTP lies, start with the step test. Zwift offers two variants for this. The normal step test increases the power by 20 watts every minute starting from 100 watts. This test feels very easy at the beginning. However, if you exceed your personal continuous aerobic power limit, it only takes a few minutes before you can no longer turn the crank. Zwift estimates the FTP at 75% of the last completed stage. So if you manage 300 watts, you get an FTP of 300 * 0.75 = 225 W. A variant of this test is the "simple" step test. Here the test starts at 50 W but ends at a maximum of 250 W (only relevant for beginners and very light athletes). The step test is simple and not very accurate, as the short step duration provokes distortions due to anaerobic energy components. However, the test is quick and is suitable for an initial assessment.
2. FTP test: standard and short version
The two FTP tests on Zwift differ in their length and structure. The aerobic performance is better measured with a longer interval than with the shorter step test.
- FTP test (standard): 1:13 h
- FTP test (shorter): 0:43 h
Both tests require a presetting of the FTP - which is why the step test should be completed first. Alternatively, you can also estimate the FTP based on previous best performances such as a race (the normalised power in a shorter race often corresponds to the FTP) or a longer, intensive climb.
Realisation: After a warm-up phase and short pre-loads, the FTP test begins with a tough five-minute interval, the purpose of which is to empty the anaerobic energy stores before the actual 20-minute test begins. If the FTP is set too high, the lights will already go out during this interval. So be careful not to set the FTP value too high! In the shorter of the two FTP tests in Zwift, the first interval is split into two and is harder than in the long test.
The actual test consists of 20 minutes of free driving. The aim here is to achieve the highest possible continuous power output over the 20 minutes. The FTP is calculated from 95% of the average performance over the 20 minutes.
Repeat the FTP test if performance drops
It is advisable to start the journey with the estimated value of the FTP. At the end of the ride, you can add another shovelful if this is possible. If the performance drops sharply in the 20 minutes, you have started off too hard and should repeat the test, as the average value will be higher if you ride steadily.
The Zwift test protocol is in line with the TOUR recommendations. The FTP performance determined in this way and the zones derived from it are easy to use. If the test does not work perfectly the first time, it can easily be repeated. Zwift automatically adjusts the FTP upwards if new 20-minute best performances are detected in freewheeling or racing.
Strengths and weaknesses of Zwift FTP tests
The FTP test is based on full exertion - generally, not just with Zwift. This is always tough and the result depends heavily on your motivation to give it your all. Exertion also means that you have to be healthy. If you never push yourself to your limits, you should have a sports medical examination beforehand.
The test should be well prepared. These things are essential alongside tried and tested Smarttrainer technology:
- Cooling (fan)
- No interference/interruption
- Motivating image/audio material
When carried out correctly, the FTP test provides valuable key performance data for the mould check.
Critics criticise the fact that the FTP test reveals nothing about the physiological causes of performance - for example, how the body provides the energy for the determined performance. This criticism is justified. The FTP extrapolated from 20 minutes to an hour can also be subject to errors. However, the values can be verified with more data from training and competition. By combining this with other tests over shorter periods of time, it is possible to make more detailed statements about the metabolism. INSCYD offers such analyses, but they also incur costs.
Alternatively or in addition, classic laboratory diagnostics are possible (lactate diagnostics and/or spiroergometry), which can also provide more information and does not always have to go as far as endurance testing. Laboratory diagnostics alone have the disadvantage that they are usually carried out too rarely - also because they are expensive. Furthermore, not all laboratory diagnostics are equally good and valuable. It is difficult to judge their quality.
The Do-it-yourself method for the FTP test allows you to simply get started and gain experience. If you test yourself regularly and ride a lot with a smart trainer/powermeter, you can easily get a pretty comprehensive picture of your performance. This can make further diagnostics superfluous. You can easily recognise whether the FTP has been tested realistically by comparing it with real data. If the FTP test predicts 250 watts and you only reach a maximum of 220 watts in one hour of uphill riding under full load, then it is clear that the test was too optimistic and fatigue was underestimated. The real FTP value is then 220 watts.
All methods together, FTP test, laboratory diagnostics and power meter data give the most complete picture. No matter how you test: The values should always be scrutinised for plausibility.
When and how often should FTP tests be carried out?
A test is recommended before every intensive training phase for orientation, a Repeat after six to eight weeks at the earliest. advisable and serves to monitor success. You should always rested and with full energy stores start testing. This means that the tests should take place during a recovery phase. The Power measurement should be as accurate as possible If necessary, use a power meter as a data source, if available. In the long term, the absolute accuracy of the power measurement is more important than you might initially think, because only reliable data has long-term value and makes even small advances visible.
As the test itself is stressful, constant FTP testing is not advisable. You have to weigh up the benefits of always using the same protocol (comparability) against the additional training load caused by the test protocol. The mental strain of engaging in an all-out test should also not be underestimated. The energy required for this may be better invested in an (indoor) race.
The FTP test can also be driven outside. But beware: most cyclists achieve slightly higher values outdoors than indoors, and higher values uphill than on flat terrain. In order to document performance progress, you should always carry out comparable tests.
Indoor FTP tests at Zwift are a good start
Zwift's FTP tests are very well suited for initial orientation and success monitoring. Anyone who rides a lot of intensive intervals and competes with a power meter will get more and often more relevant data this way than with a single FTP test. Best values for pedalling performance are usually only achieved in competition.
