Why a dollar today isn't worth the same as a dollar in the future
Present value starts from a simple idea: money available today can be invested and earn interest, so it's worth more than the same amount available only some time from now. The discount rate used in this calculation represents exactly that opportunity cost — how much the money could have earned if it had been available to invest right away. The higher the discount rate, or the further away the future payment, the smaller the equivalent present value.
Formulas used
Present value of a single payment: PV = FV ÷ (1 + rate ÷ n)^(n × years)
Present value of a series of payments: PV = payment × (1 − (1 + i)^−n) ÷ i
Where FV is the future value, n is the number of compounding periods per year (first formula) or the number of periods (second formula), and i is the discount rate per period.
Practical example: present value of a single payment
A $20,000 payment due in 5 years, discounted at a 6% annual rate compounded monthly, is worth roughly $14,828 today. In other words, receiving $14,828 now and investing it at that same rate for 5 years would produce exactly the future $20,000.
Practical example: present value of a series of payments
A series of 24 future payments of $500 each, discounted at a 1% rate per period, is worth roughly $10,622 today. This kind of calculation is used, for example, to value the right to receive a fixed monthly rent for a given period, or the present value of pension payments.
Practical example: receive today or in the future?
Between receiving $9,000 today or $10,000 in 2 years, at an 8% annual discount rate, the present value of the future $10,000 is roughly $8,573 — less than the $9,000 available now. That means, at this discount rate, it's better to take the smaller amount today, since investing it at the same rate for 2 years would yield more than the $10,000 promised in the future.
The discount rate changes the answer
The result of the "today or later" comparison depends entirely on the discount rate chosen. With a lower discount rate, the future amount loses less value when brought back to today, and can end up being worth more than the amount available right away. That's why the rate used should reflect the realistic return you could actually get by investing money available today — not an arbitrary number.
What this calculator doesn't account for
These calculations assume a constant discount rate for the entire period and don't include taxes on any earnings, inflation separate from the discount rate, or the risk that a promised future payment might not actually be paid (relevant when evaluating a third party's promise to pay). Use the results as a reference for financial decisions, adjusting the discount rate to fit the real context of the situation.