Fourteen statistics calculators built to show the formula, not just the number.
StatsCalc started as a single standard deviation calculator that kept coming up short: most versions online return one number and call it done, without saying whether that number divides by n or by n minus 1. This site exists to fix that gap across the rest of introductory statistics, sample size, p-values, confidence intervals, z-scores and probability, one calculator at a time.
Every calculator does its arithmetic in JavaScript inside your browser tab. Type a data set into the standard deviation tool and the page computes both the sample and population figures on the spot; nothing you enter is sent to a server, because there is no server in that loop to send it to. The editorial standards page lists which formula each tool implements and how it gets checked.
StatsCalc is owned and operated by Chris Terry through Encore Promotional Products, as one of a small set of calculator sites under the Encore Editorial name. Chris built the calculators and writes the guides; he is not a statistician by trade, and the site does not claim otherwise. What he checks, every time, is that a formula matches a published textbook or handbook version of that formula and that a worked example on the guide pages reproduces what the calculator returns for the same numbers. See the authors page for the specifics.
These tools are for planning, homework, and sanity-checking, not for a dissertation's statistical appendix or a clinical trial. If a result needs to hold up under peer review, run it again in R, Python, SPSS, or whatever your department already trusts, and treat StatsCalc as a fast first pass.