Cycling calculator
Normalized power calculator
Enter a ride as a handful of blocks — minutes and average watts each — and get normalized power, intensity factor and variability index. Free, instant, no sign-up.
Your ride, block by block
Optional — used for the intensity factor.
This is a segment approximation: it weights each block by its duration and cannot see the 30-second smoothing across transitions, so very short, very sharp intervals read a little high here.
Normalized power tells you what a session cost — the coach decides what the next one should be.
What is normalized power?
Normalized power is Andrew Coggan's estimate of the steady wattage that would have cost you the same physiologically as the variable ride you actually did. Average power under-reports a stop-start ride badly, because the metabolic cost of hard efforts does not scale linearly with watts — a minute at 400 W hurts far more than two minutes at 200 W help. Normalized power is what training stress score and intensity factor are both built on.
How this calculator works
The published algorithm takes a 30-second rolling average of the power file, raises every value to the fourth power, averages those, and takes the fourth root. A web form has no file to read, so this works from the blocks you type in: inside a block held at a steady wattage the rolling average is that wattage, which reduces the algorithm to a duration-weighted quartic mean — NP = (Σ duration × watts⁴ ÷ Σ duration)^0.25. The one thing it cannot model is the smoothing across a transition, so treat the figure as a close estimate rather than a replacement for analysing the file.
Reading the variability index
Variability index is normalized power divided by average power, and it describes the shape of the ride rather than its size. A well-paced time trial sits near 1.00–1.05; a hilly road race or a criterium runs 1.10–1.20 or higher. High VI on a ride that was meant to be steady is a pacing problem: you burned matches on every rise and paid for it. High VI on an interval session is simply the session doing its job.
Using NP without fooling yourself
Normalized power is unreliable over very short efforts — below about 20 minutes the fourth-power weighting exaggerates a single spike, which is why a five-minute NP means very little. It also drifts upward if you coast a lot, because zeros drag the average down while barely touching the quartic mean. Use it for whole sessions, compare like-for-like courses, and pair it with intensity factor so the number is anchored to your current threshold rather than to last season's.