Computes areas (probabilities) under an F curve. F values are never negative and the curve is right-skewed, so ANOVA and variance-ratio tests use the right tail. Its shape depends on two degrees of freedom.
The buttons above the chart choose which area is shaded and reported:
The calculator works in both directions — edit whichever value you know:
You can also drag the boundary line(s) directly on the chart. The banner beside the buttons reports the current area.
The F distribution needs two: Numerator df₁ and Denominator df₂. Set each with its number box or slider. In ANOVA, df₁ comes from the number of groups and df₂ from the total sample size.