Opportunity Cost Calculator
See what a purchase or a regular expense could be worth if you invested the money instead, in future money and in today's money.
What opportunity cost means
Every dollar you spend is a dollar you cannot invest. Opportunity cost is the value of the best alternative you gave up. This calculator takes a one-off amount and a monthly amount, and grows them at the return you choose. It also shows the result in today's money so you can see the effect of inflation.
Use it to compare, not to feel guilty. A good purchase can be worth far more than its investment value, but it helps to know the real price first.
Last reviewed November 2026. Formulas are standard and shown in the sections above; results are estimates.
Tips and common mistakes
- Use a cautious return, not the best case.
- Try small monthly amounts; they add up over decades.
- Compare the cost with how many hours of work it takes to earn.
Learn more
Frequently asked questions
Is the return guaranteed?
No. Markets move up and down, so the result is an estimate.
Why show today's money?
Prices rise over time, so future dollars buy less.
Does it include tax?
No. Taxes on investment gains would reduce the result.
Does it apply to debt?
Paying off a loan is also an investment equal to its rate, so compare that rate to the return.
Money guides for this topic
All guides →Real Return: What Fees, Tax and Inflation Take
Why a 7% headline return can feel much smaller, and how to measure growth in today's money after costs.
Read guide →What Is Net Worth and How Do You Grow It?
Assets minus debts is the one number that shows your progress. Learn how to calculate it and the levers that raise it.
Read guide →How to Save Money: 10 Practical Ways with Real Numbers
Ten proven ways to save money, each with the math showing how much you can keep every year.
Read guide →Related calculators
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Open calculator →Results are estimates and not financial advice.