Cycling FTP Test Calculator
Convert a cycling test reference power into an explicit FTP estimate, compare factor sensitivity and track change from a previous value.
Threshold testing workspace
Visible user-chosen protocol factor
Your test-based threshold estimate
237.5 W · estimated FTP
20-minute reference × 95% chosen factor
Full result table
| Test reference W | Conversion % | Estimated FTP W |
|---|---|---|
| 250 | 90 | 225 |
| 250 | 95 | 237.5 |
| 250 | 100 | 250 |
A protocol-based estimate, not a measured one-hour performance or critical power. Test preparation and ramp definitions differ. The factor is always visible and editable; changing the protocol requires checking it. No power-zone prescription or population ranking is assigned.
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How to use Cycling FTP Test Calculator
- Select whether your input represents a 20-minute average or a ramp-test reference.
- The main estimate is the reference power multiplied by your factor.
- A previous FTP is useful only when the power meter, testing conditions and protocol are comparable.
Worked example
A 250 W test reference with a 95% factor gives estimated FTP 237.5 W. Relative to a previous 220 W, that is a 17.5 W change.
Formula, accuracy & limitations
Estimated FTP = test reference watts × chosen factor / 100. Change% = 100 × (new − previous) / previous when previous > 0. Protocol selection labels the input; it does not silently change the factor.
A protocol-based estimate, not a measured one-hour performance or critical power. Test preparation and ramp definitions differ. The factor is always visible and editable; changing the protocol requires checking it. No power-zone prescription or population ranking is assigned.
These outputs use the stated model and your supplied inputs. A mathematically consistent model can still differ from personal measurements. Scenario curves and formula comparisons are not statistical confidence intervals.
Source and method context ↗Identify the test reference correctly
Select whether your input represents a 20-minute average or a ramp-test reference. A final ramp step, a best minute and a test-provider result are not automatically interchangeable. Enter the conversion factor required by the protocol you actually used instead of assuming every ramp method uses one universal percentage.
Keep the factor visible in the result
The main estimate is the reference power multiplied by your factor. The comparison shows nearby factors to make that assumption visible. These alternatives are not confidence limits, and the selector deliberately does not silently replace a factor that you entered for a different test.
Compare like with like over time
A previous FTP is useful only when the power meter, testing conditions and protocol are comparable. A change can reflect technique, calibration, fatigue or test design as well as fitness. The score does not certify what you can sustain for exactly an hour.
Distinguish a test conversion from a fitted model
A 250 W reference multiplied by 0.95 produces 237.5 W regardless of whether the report label says 20-minute or ramp. That is deliberate: the actual conversion assumption remains visible instead of changing behind the selector. A ramp protocol requiring 0.75 would instead produce 187.5 W from the same numerical reference, but only if that reference has the meaning required by that protocol. These arithmetic differences are why a protocol label alone cannot establish an accurate personal threshold.
Frequently asked questions
Is FTP the same as critical power?
They are different constructs and estimation procedures. This tool converts a protocol reference; the critical-power calculator fits multiple duration-effort pairs.
Does selecting ramp automatically set 75%?
The factor remains explicit. Ramp reference definitions vary, so you must enter the factor specified by your testing method.
Why does the previous value allow zero?
Zero means no previous comparison is available. The tool then reports no percentage change instead of dividing by zero.
Does a higher estimate prove better fitness?
Not by itself. Consistent measurement and test conditions are needed before a change is interpreted as physiological improvement.
