# How to use Confidence Interval Calculator

Enter successes and sample size to get a Wilson score interval for a survey
percentage. Choose 90%, 95%, or 99%. You can add a finite population size if you
sampled a large share of a known group.

The tool is at form.ms/tools/confidence-interval-calculator
[https://form.ms/tools/confidence-interval-calculator].


1. OPEN THE CALCULATOR

Go to the Confidence Interval Calculator
[https://form.ms/tools/confidence-interval-calculator]. Successes are the count
in the category you care about (yes, satisfied, promoters). Sample size is n.




2. ENTER X, N, AND A LEVEL

Type Successes (x) and Sample size (n). Pick 90%, 95%, or 99%. 95% is the usual
default. Leave Population size N blank unless you sampled without replacement
from a known finite group.


3. READ THE INTERVAL

You get the observed percentage plus lower and upper bounds. Wilson stays inside
0 to 100%. This page is for one share, not for NPS (a difference of two
percentages).

Nothing is uploaded. For the headline NPS number, use the NPS Calculator
[https://formms.help.center/article/1028-how-to-use-nps-calculator].