This is a web-based effect-size calculator. It is designed to facilitate the computation of effect-sizes for meta-analysis. Four effect-size types can be computed from various input data: the standardized mean difference, the correlation coefficient, the odds-ratio, and the risk-ratio. This calculator is a companion to the 2001 book by Mark W. Lipsey and David B. Wilson, Practical Meta-analysis, published by Sage. An older Excel based version of the calculator can be found at http://mason.gmu.edu/~dwilsonb/ma.html. Additional tools for performing meta-analysis can also be found at that web address.