Calculators that show their work.

Cohen's d calculator (with Hedges' g)

Compute Cohen's d and the small-sample-corrected Hedges' g (with its 95% CI) from two groups' mean, SD, and n: every step shown, Cochrane- and Hedges & Olkin-cited.

Confidence interval to standard deviation converter

Recover the standard error and standard deviation from a reported confidence interval, for a single mean or a difference in means. Shows every step with the Cochrane citation.

Hedges' g calculator

Convert Cohen's d (or raw group means and SDs) into Hedges' g, the small-sample bias-corrected effect size, with J, Var(g) and a 95% CI. Every step shown, cited.

SEM to SD converter (and back)

Convert a standard error of the mean (SEM) to a standard deviation (SD) and back, given the sample size: the √n step, with the Cochrane citation attached.

Standardized mean difference calculator

Compute the standardized mean difference (Hedges g) from two arm summaries (mean, SD and n per group) with its 95% CI and the raw mean difference in native units.

Median and IQR to mean and SD converter

Convert a median with interquartile range (Q1, Q3) and sample size into an estimated mean and SD using the Wan 2014 method, with live skew checks that tell you when the conversion is unreliable.

OR, RR, ARR and NNT calculator (2×2)

Turn a 2×2 table of events and totals into risk ratio, odds ratio, absolute risk reduction and number needed to treat, with log-scale 95% CIs, zero-cell continuity correction, and the Cochrane citation.

IQR to standard deviation converter

Convert an interquartile range (Q1, Q3) to standard deviation: SD ≈ IQR / 1.349, with the Wan 2014 small-sample correction when you give the sample size.