e rate of convergence of a limit governs the number of terms of the expression needed to achieve a given number of digits of accuracy. In the case of Viète's formula, there is a linear relation between the number of terms and the number of digits: the product of the first n terms in the limit gives an expression for π that is accurate to approximately 0.6n digits.[8][11] This convergence rate compares very favorably with the Wallis product, a later infinite product formula for π. Although Viète himself only used his formula to calculate π with nine-digit accuracy, an accelerated version of his formula has been used to calculate π to hundreds of thousands of digits.[8]