Investing term

What is Opportunity cost?

The value of what you give up when you choose one option over another.

Opportunity cost is the value of the best alternative you give up when you make a choice. Every decision to use money, time, or attention one way is also a decision not to use it another way — and the real cost of an option is what you forfeit by not taking the next-best one.

In investing it's everywhere, because every dollar in one place is a dollar not somewhere else. Cash sitting idle isn't "free" — it carries the cost of the return it could have earned invested. Thinking in opportunity-cost terms keeps you honest: the question isn't just "is this a decent option?" but "is it my best available use of this money?"

The cost of sitting in cash
$10k$15k$20know10 yrs$19.7k$10kthe gap you give upCash that earns nothing has a real cost when the market is compounding elsewhere.

$10,000 left in cash stays flat while the same money compounding at 7% reaches about $19,700. That widening gap is the opportunity cost.

For example

Leaving $10,000 in a 0% account while markets return 7% carries a $700-a-year opportunity cost — the gain you quietly forfeited.

Learn it by doing

That's Opportunity cost in theory — it clicks when you use it. Practise it hands-on in a free, interactive lesson (Stage 1, Money, Goals & Your Financial Foundation).

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Why it matters to you

Opportunity cost is the lens that turns invisible costs visible. Holding too much idle cash, hanging on to a mediocre investment out of habit, or paying down a 3% loan instead of investing at a higher expected return all look harmless until you name what you're giving up. It's also the discipline behind good diversification and rebalancing: money should sit where it earns its keep, not where it happens to have landed.

⚠ Forgetting the cost of doing nothing

Inaction feels safe because it avoids an obvious loss, but it has an opportunity cost just like any active choice. Leaving money in cash "until things settle" can quietly forfeit years of compounding. The alternative you didn't pick is still a cost, even when the choice was to sit still.

Frequently asked questions

What is opportunity cost in simple terms?

It's what you give up when you choose one option over another — the value of the best alternative you passed on. If you spend an hour or a dollar on one thing, the opportunity cost is the most valuable thing you could have done with that same hour or dollar instead.

Why does opportunity cost matter in investing?

Because every dollar can only be in one place at a time. Money in a low-return account has the opportunity cost of the higher return it could have earned elsewhere. Weighing options by opportunity cost helps you put money where it works hardest instead of where it happens to sit.

Is holding cash an opportunity cost?

Yes, when that cash could be earning more. A cash buffer for emergencies is worth its low return for the safety it provides, but excess cash held out of habit or fear carries a real opportunity cost — the compounding return it would have earned if invested.

How is opportunity cost different from a sunk cost?

Opportunity cost looks forward — what you give up by choosing one option now. A sunk cost is money already spent that you can't recover. Good decisions weigh opportunity costs and ignore sunk costs, since only future alternatives are still within your control.

Read the full guide

FoundationsShould I Pay Off Debt or Invest First?A clear framework for the debt-vs-invest decision: when to crush the debt first, when to invest alongside it, and the one move you should never skip.7 min read

Related terms

APRAnnual Percentage Rate. The yearly interest cost of a loan, including most fees.CompoundingWhen your returns earn returns of their own, so money grows faster the longer it's invested.Emergency fundCash reserved for unexpected expenses, usually 3–6 months of your usual spending.Employer matchFree money from an employer that matches part of what you contribute to a workplace retirement plan.
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