Time Value of Money
A dollar today and a dollar ten years from now are not the same amount of money — and putting a number on that difference is the foundation under almost every other calculation in finance.
What Is It
Time Value of Money (TVM) is the principle that a dollar available today is worth more than the same dollar received at some point in the future, because today's dollar can be put to work right away — invested, earning interest, or growing — while a future dollar can't start until it arrives. Comparing amounts of money from different points in time only works once both are converted to the same reference point, usually today's value, called present value. That conversion uses a discount rate, which represents what the money could otherwise have earned in the meantime.
Why It Matters
Almost any decision that spans more than one point in time relies on this idea to make a fair comparison: choosing between a lump sum and a series of payments, valuing a bond, deciding whether a future payout is actually a good deal, or projecting what a savings goal today is really worth against tomorrow's expenses. Discounting is Compound Interest run in reverse — instead of asking what a present amount grows into, it asks what a future amount is worth by removing the growth that hasn't happened yet. It's also the engine behind Net Present Value, which applies this same discounting to a whole series of future cash flows at once.
Quick Example
$10,000 promised 10 years from now, discounted at a 7% rate, is worth about $5,083 today. That's not an arbitrary haircut — it means that if you had $5,083 right now and invested it at 7%, it would grow into that same $10,000 by the time the future payment arrived. The two figures aren't different amounts of money; they're the same value, expressed at two different points on the timeline.
See how the present value changes with your own numbers: