Star formation process is slow and inefficient, meaning that the star formation timescale (the depletion time) is much longer than the free fall time, and only a very small fraction of gas is converted to stars per free fall time. In this talk, I will present estimations of the star formation efficiency per gravitational free fall time from observations of 14 nearby galaxies, with resolution matched to the typical size of a Giant Molecular Cloud. This quantity is theoretically important but so far has only been measured for the Milky Way clouds or inferred indirectly in a few other galaxies. By assuming a constant thickness of the molecular gas layer (100 pc), the median value of efficiency per free fall time in the sample is 0.7%, slightly smaller than the general consensus of 1%. Individual galaxies show different values of efficiency per free fall time, ranging from 0.3% to 2.6%. Higher efficiency per free fall time is observed in low mass galaxies, reflecting both long free-fall times and short depletion times, though both measurements are subject to biases. The dominant uncertainties of these measurements are the estimated line-of-sight depth through the molecular gas layer and the choice of star formation tracers. This study has been conducted using new, high resolution CO imaging from the PHANGS-ALMA survey.