Confidence Interval Calculator

Enter how many in the sample, the mean and standard deviation, choose a confidence level, and the calculation is done live. Read Confidence Intervals to learn more.

Standard Deviation and Mean

Use the Standard Deviation Calculator to calculate your sample's standard deviation and mean.

Caution: you should really use the standard deviation of the entire population!

But you can use the standard deviation of your sample if you have a large enough sample: at least n=30, the more the better.

How It Is Calculated

The Confidence Interval formula is

X  ±  Z s


80% 1.282
85% 1.440
90% 1.645
95% 1.960
99% 2.576
99.5% 2.807
99.9% 3.291