Opportunity cost

The receipt shows what you pay, but not what the same money could do elsewhere. Opportunity cost uses your next-best feasible alternative, not every option you reject added together. For a purchase, that alternative might be keeping money in savings; for an evening, it might be paid work or rest.

In a sentence

• "At a 5% annual yield, the opportunity cost of spending $1,000 includes $50 in forgone savings interest over one year."
• "The opportunity cost of buying the camera is what I give up from my next-best alternative, not another charge on the receipt."
• "I count the opportunity cost of Saturday's overtime as the family time I give up."

How it works

1. Identify the resource you commit. A purchase uses money; a course or extra shift uses time, and sometimes money too.
2. Name the next-best feasible alternative. Compare with what you would actually do instead, not an unavailable investment or an activity you would never choose.
3. Use the same time period. A year of owning something belongs beside a year of the alternative, with any remaining value included.
4. Separate cash payments from forgone benefits. For savings, distinguish the original money from the interest it earns; the original money is already represented by the purchase price.
5. Compare benefits as well as costs. A purchase can provide useful service or enjoyment that a savings balance does not, even when those benefits have no clear dollar value.

For money left in savings for one full year at an unchanged annual yield, with no deposits or withdrawals and ignoring taxes and fees, the interest calculation is:

One-year forgone savings interest = amount spent × annual yield

An example

You have $1,000 and choose between buying a camera and keeping the money in savings. Assume savings is your next-best alternative and pays a hypothetical 5% APY for the full year, earning $1,000 × 0.05 = $50. If you buy, assume you sell the camera at year-end for $800 after selling costs. Ignore taxes and assume no camera running costs or changes to the savings balance other than interest.

The camera's one-year ownership cost is $1,000 − $800 = $200, and forgone savings interest adds $50 to the comparison. You finish with $250 less cash than saving, since $1,050 − $800 = $250, in exchange for a year of camera use.

Why it matters

Opportunity cost changes the purchase question from whether you can pay to whether you prefer the purchase over the best alternative. A low cost per use can show that you expect to use something often, but it does not show what another use of the money would provide. Both calculations can be useful without either making the decision for you.

Annual billing raises the same question. A discount reduces the service's price, while paying upfront reduces the cash available for savings or other commitments. The comparison depends on what you would otherwise do with that cash and whether you expect to keep the service.

Opportunity cost versus an out-of-pocket expense and total cost of ownership

An out-of-pocket expense is money you actually pay; opportunity cost is value you forgo even when no payment records it. A total cost of ownership estimate combines purchase, running, and disposal costs and subtracts resale proceeds or remaining value over a stated period. Some estimates include forgone returns too, so check the assumptions before adding them.

In the camera example, do not add the entire $1,050 alternative savings balance to the $1,000 purchase price, because that counts the original $1,000 twice. Likewise, do not add the $50 of forgone interest again if your ownership estimate already includes it.

Common questions

Is opportunity cost always money? No. Time spent on one activity is unavailable for another, so the alternative might be rest, family time, study, or paid work. You can recognize that trade-off without assigning every hour a dollar value.

Is opportunity cost the sum of everything I could have done instead? No. It is the value of the next-best feasible alternative. Adding the benefits of several mutually exclusive choices exaggerates what you actually give up.

Is forgone savings interest always the right comparison? No. Savings interest fits when leaving the money in savings is your next-best alternative. If you would instead reduce debt, the relevant financial benefit may be avoided interest; if you compare investments, distinguish uncertain expected returns from guaranteed outcomes.

Does a high opportunity cost mean I should not buy? No. Opportunity cost describes a trade-off, not a rule against spending. The purchase may provide benefits you value more than the alternative, including meeting a need or freeing up time.

Go deeper

• How to decide whether a purchase is worth it adds cost per use and hours of work to the purchase comparison.
• Annual versus monthly billing compares the discount with how long you expect to keep a service.
• Savings goal calculator works out a monthly contribution or time to a goal, with savings interest counted along the way.