The margin requirement for a short iron condor is the requirement of the short credit spread on one side of the position (if both sides are the same width.  If not, use the wider side).  

 

Example:  

 

Buy to open 2 MAR 50 puts at $0.80  

 

Sell to open 2 MAR 53 puts at $1.25  

 

Sell to open 2 MAR 67 calls at $2.00  

 

Buy to open 2 MAR 70 calls at $0.75  

 

The margin requirement for this position is $600 ($300 x 2 contracts).