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Opportunity Cost

General

Opportunity Cost

The value of the next-best alternative you give up when you choose one option over another. It's not a cash expense, it's what you missed out on by not choosing differently.

Definition

Opportunity cost is what you give up by choosing one option instead of another. It doesn't show up on a receipt or bank statement, it's the value of the road not taken, and it applies to money, time, and any other limited resource.

The concept matters most when comparing financial choices. Paying off a low-interest loan early versus investing that cash, renting versus buying a home, taking a fixed deposit versus a mutual fund, in each case, the opportunity cost is the return you'd have earned from the option you skipped. The Rent vs Buy Calculator makes this concrete by projecting both paths side by side.

Unlike an accounting cost, opportunity cost never appears in a budget. It only exists as a comparison, which is exactly why it's easy to overlook.

Formula

Opportunity Cost = Return of Best Forgone Alternative − Return of Chosen Option

There's no universal formula because it depends entirely on what the alternative was. The calculation is really just: what would I have earned or saved doing the other thing instead?

Worked Example

Priya has ₹5,00,000 and is deciding between paying off a personal loan at 11% interest early or investing in an index fund expected to return 12% annually.

  • Paying off the loan early "saves" 11% guaranteed
  • Investing instead has an expected return of 12%, but with market risk
  • The opportunity cost of paying off the loan early ≈ 12% − 11% = 1 percentage point per year, in exchange for eliminating risk entirely

Whether that trade is worth it depends on Priya's risk tolerance, not just the math.

Key Things to Know

  • It's a comparison, not a cash outflow. You won't see opportunity cost as a line item anywhere, it only exists when you set two choices side by side.
  • Risk-free options still carry an opportunity cost. Even the safest investment has one, measured against whatever riskier option you passed up.
  • It applies to time as much as money. Choosing to build a feature yourself instead of buying a tool has an opportunity cost in hours, not just dollars.
  • Don't confuse it with a sunk cost. Money already spent is gone regardless of what you do next; opportunity cost is forward-looking and depends on the decision in front of you.
  • It's subjective when risk differs between options. A "higher return" alternative isn't automatically the better choice if it comes with meaningfully more risk or less liquidity.

Related Calculators

ROI Calculator →Calculate your return on investment (ROI), annualized return, and net profit. Works for stocks, mutual funds, real estate, and any investment.
Rent vs Buy Calculator →Compare the true cost of renting vs buying a home. Factor in loan payments, maintenance, rent inflation, and investment returns to make the right decision.
SIP Calculator →Calculate your SIP returns instantly. Enter monthly investment, expected return, and duration to see your estimated corpus and gains in seconds.

Frequently Asked Questions

Is opportunity cost the same as a sunk cost?
No, they're opposites in a sense. A sunk cost is money already spent that you can't get back, while opportunity cost is about a choice you're making now and what you're giving up by not picking the alternative. Sunk costs shouldn't factor into a decision; opportunity cost should.
How do I calculate the opportunity cost of buying a house instead of renting?
Compare what you'd earn investing your down payment and the rent-vs-mortgage difference in the stock market versus the equity and appreciation you'd build by owning. The [Rent vs Buy Calculator](/rent-vs-buy-calculator/) runs both paths side by side so you can see the real gap over time.
Does opportunity cost apply to time, not just money?
It applies to any limited resource. Spending three hours on one task means you can't spend those same three hours on something else, and that lost alternative is the opportunity cost of your time, even though no money changed hands.
Why does opportunity cost matter for investing decisions?
Every dollar in a low-yield savings account has an opportunity cost equal to what it could have earned in the market instead. If a savings account pays 2% and the market has historically returned 8-10%, that 6-8% gap is the opportunity cost of playing it safe, which is a valid choice, but one worth naming.
Can opportunity cost be negative?
Not really. It represents value forgone, so it's always a cost relative to the alternative. If the choice you made actually turns out worse than the alternative, that's a loss on top of the opportunity cost, not a negative opportunity cost.