Present Value Calculator

Time value of money is the principle that a given sum is worth more the sooner it arrives, because money in hand today can be put to work — invested, lent, or used to avoid borrowing — while the same sum promised for later cannot do any of that in the meantime. Present value is the tool that puts a number on exactly how much less that later sum is worth right now, by working out what amount today would grow into it at a stated rate.

This is a genuinely different question from inflation. Inflation asks how much prices will rise; present value asks how much return you are giving up by waiting. The two can be combined, but they are not the same adjustment, and conflating them is one of the more common mistakes in evaluating a future payment.

Discounting is compound interest run backwards. Where compounding starts with a sum today and asks what it becomes after growing for a number of periods, discounting starts with a sum in the future and asks what smaller amount today would be needed to reach it, growing at the same assumed rate. The higher the rate, or the longer the wait, the smaller that today-equivalent figure becomes — which is why the discount rate chosen has such an outsized effect on the result, and why the sensitivity table above exists.

The same calculation underlies a wide range of everyday and professional financial decisions.

The rate should reflect what the money could otherwise earn at a comparable level of risk — your opportunity cost, not an arbitrary figure. A higher-risk future payment generally warrants a higher discount rate, which in turn produces a lower present value, reflecting the extra uncertainty attached to actually receiving it. Because this input is a judgement rather than a measurement, running the calculation across a range of plausible rates, as the sensitivity table does, tends to be more informative than trusting a single figure.

The mathematics of discounting is old — compound interest tables have existed for centuries — but its formal use to value long streams of future income developed alongside modern economics and finance in the early-to-mid twentieth century, as economists worked out how interest rates connect the value of capital today to the income it is expected to produce later. That framework now sits underneath most professional investment appraisal, from pricing a government bond to deciding whether a company should build a new factory.