The charts presented in this paper are designed to facilitate the estimation of the number of observations per treatment required for analysis of variance tests of specified power. They are intended for use by experimenters dealing with fixed treatments effects. With these charts the experimenter may answer the following question: How many observations must I use per treatment to obtain a power of $P_1$ against alternative hypothesis $H_1$? Charts are presented for use with tests of treatments effects involving two to five levels of the treatment variable. The charts are strictly valid only for the completely randomized design; however they may be applied with relatively little error to tests of treatments effects in the randomized block and factorial designs, the latter employing a within-cells estimate of error variance.