Software mortgage and credit calculations and amortizing schedule. The credit software has unique features that let user know the true cost of their credit and optimize their mortgage payments to save money. Users start by creating a new mortgage definition. This credit definition can be saved/loaded. The software displays the amortizing and computes the true costs of the credit. It also computes the mortgage's equivalent interest rate, which is the true cost of the mortgage, including fees and credit insurance. Then, it is possible to simulate extra payments (or reducing payments) and compute the exact gain/loss corresponding to these changes. With optim-credit, it is also possible to combine several mortgages and computes the global equivalent interest rate and true costs of the credits. Optim-credit is free to use and runs under Windows XP service pack 2.