Efficient and highly accurate interconnect delay and slew computation is critical for physical synthesis and static timing analysis. Elmore delay is simple and closed-form metric, but it has too low accuracy. Some higher order moments metrics such as AWE can have high accuracy, but we cannot afford their calculation speeds. In this paper we propose two closed-form delay metrics and two closed-from slew metrics using the first three moments, which can be used for both step input and ramp input.