What is Intensity Factor?
Intensity Factor (IF) is the ratio of Normalized Power (NP) to your Functional Threshold Power (FTP): IF = NP / FTP. It provides a simple, normalized measure of how hard a workout was relative to your current fitness.
An IF of 1.0 means you rode at your threshold for the entire workout. Typical ranges are: below 0.75 for easy endurance rides, 0.75 to 0.85 for tempo efforts, 0.85 to 0.95 for threshold intervals, 0.95 to 1.05 for VO2max work, and above 1.05 for short anaerobic efforts.
IF is one of the three components of the TSS formula (TSS = IF² × hours × 100). It is also a useful sanity check: if a 3-hour ride has an IF above 0.95, either the effort was extraordinary or your FTP needs retesting.