LIMITED TIME Lifetime Deal: Get the published plan features for a $399 one-time payment. Grab the Deal →
Free Rowform tool

Free Confidence Interval Calculator

Calculate a confidence interval for a sample mean using sample size, mean, and standard deviation.

Rowform free toolPrivate · runs in your browser

How to Use This Confidence Interval Calculator

  1. Enter the sample size, sample mean, and standard deviation.

  2. Choose the confidence level appropriate for your analysis.

  3. Calculate the lower and upper bounds and margin of error.

What is a confidence interval?

A confidence interval is a range around a sample estimate. Under repeated sampling, the chosen percentage of intervals produced by the same method would contain the population mean.

The Formula

CI = x̄ ± Z × (σ ÷ √n)
Build with Rowform

Ready to create your own conversational form?

Create a beautiful, mobile-friendly survey people will want to complete, then share it anywhere and collect responses.

  • No standard monthly response cap on Rowform's free plan.
  • Create multiple forms and add the questions you need
  • No credit card required
Create your first form - free

Frequently Asked Questions

Does this use a z-score or t-score?

This tool uses z-scores. A t-interval may be more appropriate for a small sample when the population standard deviation is unknown.

How can I narrow the interval?

A larger sample or less variable data produces a narrower interval at the same confidence level.

Related Free Tools

View all tools →
NPS CalculatorCalculate your Net Promoter Score and see the split between promoters, passives, and detractors.Sample Size CalculatorEstimate how many survey responses you need for a chosen confidence level and margin of error.Chi-Square CalculatorTest whether two categorical variables are independent with a configurable contingency table.