Abstract The relationships between measurement time, travel time, and plot size are examined for simple random sampling and systematic sampling on a square lattice. The total time to estimate a stand variable within a desired level of accuracy is shown to be minimal if plot size is calculated from the formula P* = P(t/m)² where P* = optimal plot size; P = any arbitrarily chosen plot size; t = travel time between two neighboring plots of size P (the distance between plots of size P should correspond to the number of plots which provides the desired accuracy); m = plot-measurement time for a plot of size P. Forest Sci. 26:251-257.