Does Excel contain a simple interest loan calculation function built in? Or do I need to specify how exactly simple interest calculates on a per diem basis? What I am trying to do is calculate finance charge based on daily interest such as a standard auto loan contract. I am supplying the interest rate, term, and days to first payment - which in itself contains all of the necessary data for calculation (assuming excel has the loan calculation built in), however simple interest is based daily, so the calculation needs to understand days in each month, and totals days across a long period of time, and I seem to remember excel having basic loan calculation features built in, however general excel help only seems to have basic functions. What would be the best way to approach this?