NP & IF Estimator

Normalized Power (NP) is a weighted average that accounts for the physiological cost of intensity variation during a ride. Two rides might have the same average power but feel very different if one was steady and the other included repeated hard surges with coasting in between.

NP was introduced by Andrew Coggan to solve this problem. The true algorithm takes second-by-second power data, applies a 30-second rolling average, raises each value to the 4th power, averages all those values, and takes the 4th root. The result is always equal to or higher than average power.

The difference between NP and average power is expressed as the Variability Index (VI = NP / AP). A perfectly steady ride has VI = 1.0. The more variable the effort, the higher the VI.

True NP requires a power file from a cycling head unit or smart trainer. This estimator uses a different approach: you provide your average power and select a ride profile, which sets an expected Variability Index. The estimated NP is then Average Power multiplied by that VI.

This is a simplification. Real variability depends on terrain, group dynamics, traffic, and your own pacing discipline. The ride profiles provided are based on typical VI ranges observed in published analyses of professional and amateur cycling data.

Use estimated NP for approximate TSS planning when you know your average power but do not have access to a full power file. For precise training load management, direct NP from a power meter is always more reliable.

For riders with power files, head units and analysis software (TrainingPeaks, Golden Cheetah, Intervals.icu) calculate true NP automatically. The full algorithm processes every data point:

Metabolic cost increases disproportionately with intensity. Riding at 400 W for 30 seconds and then coasting for 30 seconds costs more energy than riding steadily at 200 W, even though the average power is the same. This is because energy systems operate non-linearly at higher intensities.

NP captures this non-linearity. It tells you what steady power would have produced the same physiological cost as your actual variable effort. This makes NP the correct input for TSS calculations and pacing analysis.

For steady rides (time trials, controlled endurance), NP and average power are nearly identical. For variable rides (criteriums, group rides, hilly routes), the difference can be substantial.

Intensity Factor helps you classify a ride and check pacing against intentions. The table below shows typical IF ranges for common cycling activities, assuming your FTP is current and NP is accurately measured or reasonably estimated.

If your IF consistently exceeds the expected range for a given ride type, your FTP may need updating. Conversely, if recovery rides consistently show IF above 0.70, you are likely riding too hard for the intended purpose.