What is Normalized Power (NP)?
Normalized Power (NP) is a weighted power metric for cycling developed by Dr. Andrew Coggan. NP reflects the true physiological cost of a workout better than simple average power because it accounts for the disproportionately high metabolic cost of power variability.
How to Use the NP Calculator
Paste power data (one value per second) separated by commas or upload a FIT file from your bike computer. The calculator applies the standard NP algorithm: 30-second rolling average, raise to the 4th power, take the mean, and extract the 4th root. It also displays average power and Variability Index (VI).
Why Use Normalized Power?
- Assess the true physiological cost of a workout or race
- Calculate TSS (Training Stress Score) for training load management
- Compare workouts with different power variability patterns
- Evaluate pacing strategy effectiveness through Variability Index
Frequently Asked Questions about NP
How is NP different from average power?
Average power is a simple arithmetic mean of all values. NP accounts for the biological fact that short bursts of high power create disproportionately high metabolic stress. NP is always >= average power, and the gap grows with more variable riding.
What is Variability Index (VI)?
VI = NP / Average Power. A VI near 1.0 indicates steady power output (typical for time trials or indoor riding). VI > 1.05 indicates high variability (criteriums, group rides, hilly terrain). For optimal flat-course pacing, aim for VI < 1.05.
How much data is needed for NP calculation?
A minimum of 30 seconds of power data (30 points at 1 Hz). For reliable results, analyze workouts of 20+ minutes. Data should be recorded at 1 Hz (one sample per second), which is standard for most bike computers.