Confidence Interval Calculator

Q: When should I use Z vs. T distribution?

Use the Z-distribution if the population standard deviation is known and the sample size is large (n ≥ 30). Use the T-distribution when the population standard deviation is unknown and the sample size is small (n < 30).

Q: Can I use this for survey data?

Yes! It’s perfect for estimating confidence intervals for proportions based on survey responses.

Use the free Confidence Interval Calculator by Calculator Hub HQ to quickly calculate the confidence interval for a population mean or proportion using sample data. Ideal for students, researchers, and data analysts who need accurate and reliable statistical insights.

What is a Confidence Interval Calculator?

A Confidence Interval Calculator is a statistical tool used to estimate the range within which a population parameter (like a mean or proportion) is likely to fall, based on sample data. The result is expressed as a confidence level—usually 90%, 95%, or 99%—indicating the degree of certainty that the true value lies within that range.

At Calculator Hub HQ, our tool helps you instantly compute confidence intervals for:

Population means (with known or unknown standard deviation)
Proportions
Large or small sample sizes
Z-scores and t-scores based on sample characteristics

Confidence Interval Calculator

Results

Why Use Calculator Hub HQ’s Confidence Interval Calculator?

Accurate Statistical Results – Supports both Z and T distributions
Multiple Confidence Levels – 90%, 95%, 99%, or custom
Supports Means & Proportions – Flexible calculation options
Step-by-Step Explanation – Understand how the interval is formed
100% Free and User-Friendly – Works on desktop and mobile devices

Whether you’re writing a research paper, conducting a survey, or analyzing business data, this calculator provides fast and reliable statistical output.

What You Can Calculate:

With the Confidence Interval Calculator, you can find:

Confidence interval for a population mean (with known/unknown standard deviation)
Confidence interval for a population proportion
Margin of error
Standard error
Z-value or t-value based on your inputs

How to Use the Confidence Interval Calculator:

Select what you’re calculating – Mean or Proportion
Enter sample size, sample mean/proportion, and standard deviation (if needed)
Choose your desired confidence level (e.g., 95%)
Click “Calculate” – Get your confidence interval and margin of error instantly

Optional: Adjust the confidence level manually to fit your academic or research requirements.

Example Use Case:

If you have a sample mean of 70, standard deviation of 10, and sample size of 100, the calculator will provide the 95% confidence interval around the mean, such as:

Confidence Interval: (68.04, 71.96)
Margin of Error: ±1.96

Frequently Asked Questions

What is a confidence interval?

A confidence interval is a range of values, derived from sample data, that likely contains the true population parameter. It provides a measure of certainty in statistical estimates.

When should I use Z vs. T distribution?

Use the Z-distribution if the population standard deviation is known and the sample size is large (n ≥ 30). Use the T-distribution when the population standard deviation is unknown and the sample size is small (n < 30).

Can I use this for survey data?

Yes! It’s perfect for estimating confidence intervals for proportions based on survey responses.

Take the Uncertainty Out of Your Statistics

Whether you’re performing academic research, analyzing data, or completing statistical homework, the Confidence Interval Calculator by Calculator Hub HQ helps you produce professional-level results with speed and accuracy.

Start calculating now—100% free, fast, and designed for statistical confidence.