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Finance Calc Kit
Investments

Opportunity Cost

Calculate the opportunity cost of spending money now versus investing it to understand the trade-off between consumption and investment.

Spending vs investing

$
%
years
%
%

Inflation-adjusted value if invested

$15,257.60

If invested for 2 years instead of spent

Forgone earnings

$926.36

Nominal investment growth on principal

Tax on gains

$203.80

Estimated capital gains tax

Total after tax

$15,722.56

Principal plus after-tax earnings

Inflation drag

$464.96

Purchasing power lost to inflation

Where the invested value goes

  • Principal$15,000.0095.4%
  • After-tax earnings$722.564.6%

How we calculated this

Open to see each step from your inputs to the result.

  1. 1. Compound forgone investment earnings

    E=P×[(1+r12)12y−1]E = P \times \left[\left(1 + \frac{r}{12}\right)^{12y} - 1\right]

    Forgone earnings = $15,000.00 * [(1.00^24) - 1] = $926.36

  2. 2. Apply tax on capital gains

    Eafter tax=E×(1−t)E_{\text{after tax}} = E \times (1 - t)

    After-tax earnings = $926.36 - ($926.36 * 22.00%) = $722.56

  3. 3. Add principal for total nominal savings

    FVnominal=P+Eafter taxFV_{\text{nominal}} = P + E_{\text{after tax}}

    Total savings after tax = $15,000.00 + $722.56 = $15,722.56

  4. 4. Adjust for inflation

    FVreal=FVnominal×(1−i12)12yFV_{\text{real}} = FV_{\text{nominal}} \times (1 - \frac{i}{12})^{12y}

    Inflation-adjusted value = $15,722.56 * (1.00^24) = $15,257.60

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What is opportunity cost?

Opportunity cost is the value of the next best alternative you give up when making a financial decision. Every dollar spent today could have been invested instead, earning compound returns over time. This calculator quantifies that trade-off by projecting how much your money would grow if invested, after taxes and inflation.

Whether you are deciding on a major purchase, evaluating a career change, or weighing lifestyle spending against long-term savings, understanding opportunity cost helps you make informed trade-offs. To model compound growth with flexible contribution schedules, use the compound interest calculator. For a full portfolio projection with recurring deposits and inflation adjustments, try the investment calculator. To compare gross profit margins on products you sell instead of spending, use the margin calculator.

How forgone investment earnings are calculated

The calculator compounds your forgone principal monthly at the annual return rate you provide, then applies capital gains tax and inflation adjustment:

E=P×[(1+r12)12y−1]E = P \times \left[\left(1 + \frac{r}{12}\right)^{12y} - 1\right]

After-tax earnings reduce the tax rate on gains, and the total nominal value (principal plus after-tax earnings) is deflated by monthly inflation:

FVreal=(P+Eafter tax)×(1−i12)12yFV_{\text{real}} = (P + E_{\text{after tax}}) \times \left(1 - \frac{i}{12}\right)^{12y}

Worked example

Suppose you spend $15,000 on a purchase instead of investing it at 3% annually for 2 years, with a 22% tax on gains and 1.5% annual inflation.

  • Forgone earnings = $15,000 * [(1.0025)^24 - 1] = $926.36
  • Tax on gains = $926.36 * 22% = $203.80
  • Total after tax = $15,000 + $722.56 = $15,722.56
  • Inflation-adjusted value = $15,257.60 in today's dollars

The real opportunity cost of spending that $15,000 is roughly $256 in lost purchasing power beyond the principal, or about $721 in after-tax investment earnings you forgo.

Frequently asked questions

Does opportunity cost include the principal?
This calculator shows both forgone earnings and the inflation-adjusted total value if you had invested the principal. The headline result reflects the full inflation-adjusted amount you would have had, not just the earnings portion.
What return rate should I use?
Use the expected return of the investment you would have chosen instead of spending. Conservative savers might use a high-yield savings or bond fund rate, while long-term investors might use historical equity averages. Match the rate to your actual alternative.
How is inflation handled?
The calculator deflates the after-tax nominal balance using monthly inflation compounding. This shows purchasing power in today's dollars, which is more useful for long-term decisions than nominal balances alone.
Are results stored on a server?
No. All math runs in your browser. Nothing is sent to the server.
Can I share my scenario?
Yes. Changing the fields updates the page URL so you can copy and share your inputs.

Resources and references

The formulas and methods in this calculator were checked against these independent sources.