Determining static timing analysis margin on non-controlling inputs of clock shaping and other digital circuits using reverse merge timing includes: selecting one or more circuits within the logic design having a plurality of inputs and using reverse merge; identifying a controlling input of the selected circuit from among this plurality of inputs; and determining for at least one non-controlling input of the circuit, a timing value that may be used to drive design optimization based on the difference between arrival times of the controlling and non-controlling inputs.