We present a formula of short-circuit power dissipation for static CMOS logic gates. By representing short-circuit current by a piece-wise linear function and considering a current flowing from input node to output node through gate capacitances, the accuracy is improved significantly. The error of our formula in a CMOS inverter is less than 15% from circuit simulation in many cases of our experiments. A improved circuit simulation technique for short-circuit power dissipation is presented. Since this formula calculate the short-circuit power dissipation accurately and quickly, it will be applied to power sensible CAD tools.