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.

How It Is Calculated

The Confidence Interval formula is

X  ±  Z s
√(n)

Where:

  • X is the mean
  • Z is the Z-value from the table below
  • s is the standard deviation
  • n is the number of samples
  Z
80% 1.282
85% 1.440
90% 1.645
95% 1.960
99% 2.576
99.5% 2.807
99.9% 3.291