Have you ever heard the attorneys on TV say "we don't get paid unless you get paid"? If you have, you heard a description of a contingency fee.
A contingency fee is similar to a sales commission. The salesman earns his living off of the sales of the product. Likewise, attorneys who represent clients on contingency earn their living from the final settlement or verdict in your case.
A contingency fee is determined by percentages. Usually in these fee arrangements, the attorney also agrees to pay all costs associated with your case. This is a huge financial risk for the attorney because no case is a guaranteed winner. Attorneys routinely pay case costs equalling thousands, hundreds of thousands or millions of dollars without a guarantee the attorney will get the money back.
Because of this financial risk taken by the attorney, the contingency fees range from 30% to 50% depending on the nature of the case and the qualification of the attorney.