I got an error when i am trying to add fomrula in formula field.

Error: Compiled formula is too big to execute (5,480 characters). Maximum size is 5,000 characters

My formula is 

```
(ED__c+Service_Tax__c+Total_Site_Work_Price1__c+Total_Selling_Price_Based_on1__c )*WCTper__c

```

In this formula ED\_\_c, Total\_Site\_Work\_Price1\_\_c, Total\_Selling\_Price\_Based\_on1\_\_c are also Formula fields. And these formulas are also contain fomrula fields.

How can i calculate the formula..?