APA 7 asks for it next to your p: compute Cohen's d from means and SDs, a t or an r; partial eta squared from an F; and the odds ratio from a 2×2 table.
What a d of 0.2, 0.5 or 0.8 means, and why those cutoffs do not work the same in every field, is in the effect size interpretation guide. How to write it in your Results section, with its confidence interval, is in how to report Cohen’s d in APA 7. And if the study you want to compare reports another metric (r, η², an odds ratio), the effect size conversions turn it into the one you need, with its formula and its assumption.
If you use it in your thesis or in a paper, cite it so that readers of your Methods section know how the calculation was done.
Ciudad-Fernández, V. (2026). Effect size calculator [Web application]. Ciudad Science. Retrieved October 18, 2026, from https://analisisdedatospsicologia.com/en/tools/effect-size-calculator
For your Methods section: Effect sizes and their confidence intervals were computed following Lakens (2013), using the Ciudad Science effect size calculator (Ciudad-Fernández, 2026).
@misc{ciudadfernandez2026tamanoefecto,
author = {Ciudad-Fern{\'a}ndez, V{\'i}ctor},
title = {{Effect size calculator}},
year = {2026},
publisher = {Ciudad Science},
howpublished = {Web application},
url = {https://analisisdedatospsicologia.com/en/tools/effect-size-calculator},
urldate = {2026-10-18},
note = {Accessed 2026-10-18},
}