if you go to the amex site there is a link that says check my spending ability. 

or you could call and ask a rep on customer service  which they usually just use the same thing. 

Current: EQ FICO 690, TU FICO 692, Walmart TU 737 EX FICO 726 Amex Pull(1/1/13) Starting total revolving credit: $2600 | Current total revolving credit: $21,600 Inquiries (12 Months): EQ 6 TU 4 EX 5 | Most Recent: 8/30/2012

2013 Goals: Freedom Signature Costco:True Earnings

Amex Zync(Unicorn) Chase Freedom$1500 Citizens Mastercard$5000