If the PQ phase transition happens after inflation, the axion energy density will have density fluctuations of order one. The size of the fluctuations is set by the horizon size at the QCD phase transition. Those fluctuations lead to the formation of gravitationally bound objects called miniclusters. A significant fraction of axion dark matter bound in miniclusters would have severe implication for axion dark matter search experiments. We present a semi-analytic method to calculate the power sepctrum of the axion miniclusters and provide an estimate for the mass function at the time of matter-radiation equality.