Estimate confidence intervals for statistical data.
CI = x̄ ± Z × (σ/√n)
The confidence interval calculator helps you estimate the uncertainty around a sample statistic by producing a defensible range that likely contains the true population value. With clear explanations, step-by-step logic, and links to the best tool types, you’ll learn not only how to compute intervals but also how to interpret them responsibly for reports, presentations, or classroom examples.
A confidence level calculator explains the selected probability (for example, 95%) that an interval method will succeed over many repetitions. Pair that with a general math calculator to compute sums, standard errors, or quick conversions,both reduce arithmetic errors and speed up your workflow. This combination is especially helpful when teaching or validating results before publication.
Start by identifying your sample statistic (mean or proportion), sample size, and whether population variability is known. Choose a z-based method for large samples with known sigma or a t-based method when sigma is unknown. Calculate the standard error, multiply by the critical value, and add/subtract from the point estimate to find upper and lower bounds. Following these steps will let you interpret the interval and communicate uncertainty clearly.
When assumptions are violated or inputs are missing, specialized methods exist: