WAAO FINANCIAL CALCULATOR
Instructions: Type in known values, then press
Calculate for the desired unknown.
Remember to use negative
values for owed balances and money paid to the account, positive
values for balances in your favor and money withdrawn from the account.
Also, enter the interest rate per period, not
per year. If you are making monthly payments and have an annual interest
rate, divide the annual rate by 12 (and see my note at the bottom of this
page). Thus, an 8% annual rate would be entered as 8/12 or .666667... (either
form is accepted). All fields must be filled in, use zeros if necessary.
The variables used are:

pv (present value) = The starting balance in an account. This number
can be zero, positive, or negative (as when you have taken a loan).

fv (future value) = The ending balance after a certain number of
payment periods (np).

np (number of periods) = The number of payment periods, usually
expressed in months.

pmt (payment) = The amount of each periodic payment

ir (interest rate) = The interest rate on the account per period.