Milliwatts to ergs per second conversion calculator shown above calculates how many ergs per second are in 'X' milliwatts (where 'X' is the number of milliwatts to convert to ergs per second). In order to convert a value from milliwatts to ergs per second (from mW to erg/s) just type the number of mW to be converted to erg/s and then click on the 'convert' button.