Investment Calculator — ROI, Annualised Return, and How Much to Save
Work out the return on an investment (total and per year), or the monthly amount needed to hit a savings goal by a date.
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Two calculators for the questions the compound-interest page does not answer. Return on investment: you put money in and later took (or could take) money out — what did it earn, in total and per year? The annualised figure (CAGR) is the one that lets you compare a three-year property gain with a five-year fund. Reach a goal: you want a certain amount by a certain year — how much do you need to put away each month, given what you have already and the return you expect?
How to use Investment Calculator
- ROI tab: enter what you invested, what it is worth now (or sold for), and how long you held it. Total return, gain, CAGR and the multiple appear instantly.
- Goal tab: enter the target, the years, the expected annual return and anything already saved. The monthly amount and a year-by-year table appear.
ROI versus annualised return
Return on investment is simply gain divided by cost: put in 10,000, now worth 15,000, ROI 50%. It says nothing about time — 50% in one year is spectacular, 50% over fifteen years is worse than a savings account. The compound annual growth rate (CAGR) fixes that: it is the steady yearly rate that would have turned the start value into the end value over the holding period. 10,000 → 15,000 over three years is a CAGR of 14.5%; over ten years, 4.1%. Always compare investments by CAGR, and compare it with what a broad index fund returned over the same years before feeling clever.
What the goal calculation assumes
Money is added at the end of each month and grows at the stated annual rate compounded monthly; the amount already saved grows on its own first, and the monthly figure only has to cover the rest. The rate is the part to be careful with: 7% is a common long-run assumption for a diversified stock portfolio before inflation, roughly 4–5% after it; a savings account is whatever it pays today. Run it with two or three rates and plan for the pessimistic one — a goal reached late is a smaller problem than one missed entirely.
Things this deliberately leaves out
- Taxes and fees — they depend on the account and the country, and a 1% annual fee takes roughly a quarter of the final balance over thirty years. Subtract fees from the rate you enter.
- Inflation — enter a real (after-inflation) rate if you want the goal in today's money.
- Volatility — real returns arrive in lumps, not smoothly. The average is right; any given year is not.
For a projection with a fixed monthly contribution and a chart, use the compound interest calculator; for pensions specifically, the retirement calculator; for loans, the loan calculator.
Frequently asked questions
What is a good ROI?
Judge by the annualised figure. A broad stock-market index has returned roughly 7–10% a year over long periods before inflation; anything consistently above that involved extra risk or luck. A "50% ROI" is meaningless without the holding period.
How is CAGR calculated?
(final ÷ initial)^(1 ÷ years) − 1. It is the constant annual rate that would produce the same end result. For a holding period under a year, CAGR is extrapolated and can look absurd, so the tool shows the total instead.
What return rate should I assume for a goal?
Depends on where the money goes: a savings account pays whatever it pays today; a diversified stock portfolio has averaged around 7% a year before inflation over decades, with wide swings. Use a lower figure than you hope for, and subtract fund fees.
Does the goal calculation include what I already have?
Yes. The existing amount grows at the same rate, and the monthly contribution only has to make up the difference. If the existing amount alone reaches the goal, the monthly figure is zero.
Are taxes and inflation included?
No. Enter an after-tax, after-fee rate; for a goal in today's money, use a real rate (nominal minus inflation, roughly 2–3 points lower). Tax treatment depends on the account and the country.