Confidence Interval Calculator

Sample Mean (x̄):

Standard Deviation (σ):

Sample Size (n):

Confidence Level:

How to Use the Confidence Interval Calculator

What is a Confidence Interval Calculator?

A Confidence Interval Calculator is a statistical tool that estimates the range in which the true population mean is likely to fall, based on sample data. It's widely used in research, science, business, and data analysis to infer the reliability of a sample estimate.

How to Use the Calculator (Step-by-Step)

Step 1: Enter the Sample Mean (x̄)
This is the average value from your data sample. For example, if you surveyed 100 people and the average income was $52,000, you would enter 52000.

Step 2: Enter the Standard Deviation (σ)
This is a measure of spread in your data — how much the data varies from the mean. If you don't know it, you can estimate it or use the sample standard deviation.

Step 3: Enter the Sample Size (n)
How many observations or data points are in your sample? Enter that number.

Step 4: Select Confidence Level
Choose how confident you want to be in the result. The most common levels are:

90% — More narrow, but less confidence
95% — Standard in most studies
99% — Very high confidence, but wider range

Step 5: Click “Calculate Confidence Interval.”
The calculator will display the interval as:
(Lower Bound, Upper Bound)

Example Use Case

Imagine you're testing average delivery time for your logistics company.

Sample Mean = 4.2 days
Standard Deviation = 1.1 days
Sample Size = 64
Confidence Level = 95%

The calculator might show:
(3.97, 4.43)
→ This means you're 95% confident that the true average delivery time is between 3.97 and 4.43 days.