How many AC amperes are there in DC amperes

You can say that the DC ampere value of current is equal to the root mean square value of an AC current of the same magnitude. The AC current changes its value from Positive Peak to Negative Peak in a cycle and the root mean square value or an Irms value is the Peak Value divided by Sqrt of 2 or = 1.414

So I peak = Irms / 1.4142

Hence whicle calculating DC amperage from AC amperage you have to consider the following terms :
AC Amperage
AC Volatage
Wattage
DC Voltage

You can use an online tool to convert this please follow the link : http://www.batterystuff.com/kb/tools/ac-to-dc-amperage-conversion-run-through-an-inverter.html