Investment Calculator
Project an investment forward with regular contributions, and see it in real terms after inflation.
Please note: Projections are illustrative, not financial advice. Investment returns vary and past performance does not predict future results.
What the Investment Calculator does
This projects an investment forward from a starting balance plus regular monthly contributions. The inflation field converts the result into today's purchasing power, which is usually the number that actually matters for planning. Contributions here are fixed at a monthly cadence — for a schedule that steps up each year, or that pays quarterly or annually, the investment growth calculator models the year-by-year path instead.
Formula
FV = P(1 + r)ⁿ + PMT × ((1 + r)ⁿ − 1) ÷ rwhere r = expected annual return ÷ 12 and n = number of monthsReal value = FV ÷ (1 + inflation)ᵗReal return = (1 + nominal) ÷ (1 + inflation) − 1
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Initial investment | selected currency | Optional | Accepts 0 or more. |
| Monthly contribution | selected currency | Optional | Accepts 0 or more. |
| Expected annual return | % | Yes | — |
| Investment period | years | Yes | Accepts more than 0, up to 100. |
| Inflation rate | % | Optional | Optional — shows the result in today's money. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Currency.
- Enter Expected annual return and Investment period.
- Optionally add Initial investment, Monthly contribution and Inflation rate.
- Select Calculate.
Worked example
$5,000 to start, $500 a month, 8% return, 25 years, 3% inflation.
- Initial
- 5000
- Monthly
- 500
- Rate
- 8
- Years
- 25
- Inflation
- 3
$512,214.08 nominally, or $244,636.30 in today's money after 3% inflation — $155,000 of that was contributed, the rest is growth.
Reading the result
- The projected value and the inflation-adjusted value answer different questions: the first is what the account balance will actually show, the second is what that balance could buy at today's prices — a nominal gain can still represent a real loss in purchasing power if the return doesn't outpace inflation.
Common mistakes
- Comparing this calculator's nominal projected value against a goal expressed in today's money without checking the inflation-adjusted figure — the two are not the same number, and the gap widens the longer the time horizon runs.
Frequently asked questions
What return should I assume?
Historically broad equity indices have averaged roughly 7–10% before inflation over long periods, but no future return is guaranteed. Running a conservative and an optimistic case is wiser than picking one number.
Why does inflation matter so much?
At 3% inflation, prices roughly double every 24 years. A large nominal balance decades away buys far less than the number suggests.