What is opportunity cost in simple terms?

What you give up by choosing one option over another — the value of the best thing you could have done instead with the same time or money.

How is opportunity cost different from sunk cost?

Opportunity cost is about the future alternative you forgo; sunk cost is money already spent and unrecoverable. One should guide decisions; the other should be ignored.

How do you use opportunity cost in decisions?

Compare each option against the best alternative use of the resource, not against doing nothing — the real cost is the foregone best option.

Opportunity cost

Economics

Opportunity cost is the value of the best alternative you give up when you make a choice. The true cost of anything isn’t just its price — it’s everything you could have done with the same time, money, or attention instead.

How it works

Every “yes” is a “no” to everything else you could have done with that resource. Reckoning the foregone best alternative reveals the real cost the sticker price hides.

How to use it

Judge a purchase or commitment against the best other use of that money or time — not against zero.
When something is “free,” ask what your time spent on it is worth elsewhere.
Prioritise by comparing alternatives, not by whether something is “worth it” in isolation.

Worked example

A “free” two-hour meeting isn’t free. Those two hours could have shipped a feature, closed a sale, or rested you for tomorrow. The meeting’s real cost is the most valuable of those foregone alternatives.

Where it fails

Over-applied, it breeds paralysis and FOMO — every choice mourns infinite alternatives. Reserve it for significant allocations of time and money, not every small decision.

The deeper point

The most expensive costs never appear on any invoice. Opportunity cost is invisible by design — which is exactly why it dominates the decisions people get most wrong, and why "but it was free" is so often a trap.

Frequently asked

What is opportunity cost in simple terms?: What you give up by choosing one option over another — the value of the best thing you could have done instead with the same time or money.
How is opportunity cost different from sunk cost?: Opportunity cost is about the future alternative you forgo; sunk cost is money already spent and unrecoverable. One should guide decisions; the other should be ignored.
How do you use opportunity cost in decisions?: Compare each option against the best alternative use of the resource, not against doing nothing — the real cost is the foregone best option.

Second-order thinking Margin of safety Sunk-cost fallacy Loss aversion

Editorial synthesis © ReadGlobe 2026, drawing on the mental-models tradition (Charlie Munger, Farnam Street) and the primary sources for each model. · Last reviewed 2026-05-29.