Abstract. In this paper, we generalize a well-known estimate of ColdingMinicozzi for the extinction time of convex hypersurfaces in Euclidean space evolving by their mean curvature to a much broader class of parabolic curvature flows.It is well known that a convex closed hypersurface in R n+1 evolving by its mean curvature remains convex and vanishes in finite time. In [1], B. Andrews showed that the same holds for a much broader class of evolutions. T. H. Colding and W. P. Minicozzi in [7] give a bound on extinction time for mean curvature flow in terms of an invariant of the initial hypersurface that they call the width. In this paper, we generalize this estimate to the class evolutions considered by Andrews: All functions F in this class are assumed to be either concave or convex. In the concave case, we require an a priori pinching condition on the initial hypersurface M 0 . In the case of convexity a pinching condition is not needed, and we can take C 0 = 1 above. This class is of interest since it contains many classical flows as particular examples, such as the n-th root of the Gauss curvature, mean curvature, and hyperbolic mean curvature flows. The key to arriving at our estimate on extinction time is a uniform estimate on the rate of change of the width, for which preservation of convexity of the evolving hypersurface is fundamental.We also study flows which are similar to those considered by Andrews in [1], except that we allow for higher degrees of homogeneity. The motivation for this consideration is that the degree 1 homogeneity condition on the flows given in Andrews' paper excludes some naturally arising evolutions, such as powers of mean curvature, for which preservation convexity and extinction time estimates are known