Revolving loans are provided at a fixed maximum limit, which is reduced by the amount of any drawings and reinstated each time the loans drawn are repaid and available for a fixed period of time (usually one, two or three years). Interest is calculated based on an agreed fixed or floating rate on the amount drawn and is accrued over the loan period (usually three months or six months). A commitment fee is generally charged on the unutilised portion of the total facility on a daily basis, and calculated at an agreed rate and paid quarterly. The principal may at the borrower's option be repayable in whole or in part at the end of each interest period.