功率重量比（或比功率，功率质量比，简称功重比、pwr）是一个用于引擎间比较的参数。功重比是衡量引擎实际性能的指标，也用作一整个载具的性能尺度。计算上，功重比不考虑载具大小及其带来的空气阻力等因素，直接用引擎功率除以载具质量而得。标签上的功重比常常是制造商测量后选取的峰值，但在实际使用中数值却是时常变化的，并且这些变化将会影响实际性能。

功重比的倒数，即重量功率比（功率载荷）用于飞机、汽车等各种载具间的比较。

另外，实践中飞机、火箭等主要以射流反冲为动力的载具也常用推重比衡量发动机性能。

Power-to-weight ratio (or specific power or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power source. It is also used as a measurement of performance of a vehicle as a whole, with the engine's power output being divided by the weight (or mass) of the vehicle, to give a metric that is independent of the vehicle's size. Power-to-weight is often quoted by manufacturers at the peak value, but the actual value may vary in use and variations will affect performance.