Ftp Calculator
Estimate Functional Threshold Power from 20-minute or 8-minute cycling tests. Enter values for instant results with step-by-step formulas.
Formula
FTP = Test Average Power x Adjustment Factor (0.95 for 20-min, 0.90 for 8-min)
FTP is estimated by multiplying the average power from a shorter test effort by an adjustment factor that accounts for anaerobic contribution. The 20-minute test uses 0.95 and the 8-minute test uses 0.90. Watts per kilogram divides FTP by body weight in kilograms.
Worked Examples
Example 1: 20-Minute FTP Test
Problem: A cyclist averages 260 watts during a 20-minute test and weighs 72 kg. Calculate FTP, watts per kilogram, and training zones.
Solution: FTP = 260 x 0.95 = 247 watts\nW/kg = 247 / 72 = 3.43 W/kg\nZone 2 (Endurance) = 247 x 0.56 to 0.75 = 138-185W\nZone 4 (Threshold) = 247 x 0.91 to 1.05 = 225-259W\nSweet Spot = 247 x 0.88 to 0.93 = 217-230W
Result: FTP: 247W | 3.43 W/kg (Cat 4) | Sweet Spot: 217-230W
Example 2: 8-Minute FTP Test
Problem: A cyclist averages 290 watts during an 8-minute test and weighs 68 kg. Calculate FTP and classification.
Solution: FTP = 290 x 0.90 = 261 watts\nW/kg = 261 / 68 = 3.84 W/kg\nClassification: Cat 3 (3.5-4.0 W/kg range)\nThreshold zone = 261 x 0.91 to 1.05 = 238-274W
Result: FTP: 261W | 3.84 W/kg (Cat 3) | Threshold: 238-274W
Frequently Asked Questions
How do I perform a 20-minute FTP test correctly on a bike?
A proper 20-minute FTP test follows a specific protocol to produce reliable results. Begin with a 20-minute warmup that includes gradually increasing effort and a few short high-intensity efforts to open up the legs. Then ride a 5-minute all-out effort to pre-fatigue your anaerobic system so it does not inflate your 20-minute result. Recover easily for 5 minutes. Then ride as hard as you can sustain for exactly 20 minutes, aiming for the highest average power you can hold without blowing up. Your FTP is calculated as 95 percent of that 20-minute average power. Perform the test on the same route or trainer each time for consistency. Avoid testing when fatigued, dehydrated, or underfueled, as these factors will produce artificially low results.
Can I estimate FTP without doing a formal test?
While a formal test provides the most accurate FTP measurement, several alternative estimation methods exist. Your best average power from a recent hard group ride or race lasting 45 to 75 minutes can serve as a reasonable FTP estimate. Ramp tests, offered by platforms like Zwift and Sufferfest, estimate FTP by finding the power at which you can no longer continue during a progressively harder effort and multiplying by approximately 0.75. Some power meters and smart trainers have built-in FTP detection algorithms that analyze your ride data over time. You can also estimate from heart rate data if you know your lactate threshold heart rate and have corresponding power data from past rides. These methods are less precise than a dedicated test but provide useful starting points for zone-based training.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
What formula does Ftp Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
Can I use the results for professional or academic purposes?
You may use the results for reference and educational purposes. For professional reports, academic papers, or critical decisions, we recommend verifying outputs against peer-reviewed sources or consulting a qualified expert in the relevant field.