Cohen's d Effect Size Calculator

Your details

Pooled SD is the standard formula. Glass delta uses only the control group SD. One-sample compares a single group mean to a known population value.
Mean of group 1 (or your sample mean in one-sample mode).
Standard deviation of group 1 (or your sample SD in one-sample mode).
Number of observations in group 1 (used for accurate pooled SD weighting).
Mean of group 2 (control or comparison group).
Standard deviation of group 2.
Number of observations in group 2.
Cohen's dSmall effect
0.3446

Standardised mean difference (effect size)

Pooled SD14.5086
r (correlation equivalent)0.1698
|d| (absolute)0.3446
0.3446 d
Negligible<0.2Small0.2-0.5Medium0.5-0.8Large0.8+

Cohen's d = 0.3446 (Small effect)

  • The absolute effect size is 0.345, which falls in the "Small" range by Cohen's (1988) conventional benchmarks.
  • Group 1 scored higher than Group 2 by 0.345 pooled standard deviations.
  • The equivalent point-biserial correlation is r = 0.170, explaining about 2.9% of variance.

Next stepA small effect is real but modest. It may require a larger sample to detect reliably; run a power analysis if you are still designing the study.

 = Powered by OnlyCalculators