Assumptions. Interest compounds monthly and contributions are added at the end of each month. Figures are before tax and inflation — real returns are lower once both are counted. This is an estimate for planning, not a guarantee of any return.
This is one number. Your real plan has many.
Manticore Finance runs this projection on your actual portfolio — with real market history, sequence-of-returns risk, fees and tax — not a single flat rate.
How compound interest works
Compound interest is interest earned on your interest. Each period, the return is calculated on everything you hold — your original money, your contributions, and every bit of interest added so far — so the balance grows faster the longer it runs. Time is the biggest lever: the same rate over 30 years produces far more than over 10, because the later years compound on a much larger base.
The formula behind the number above is the future value of a starting sum plus a stream of regular deposits: FV = P(1 + i)N + PMT · ((1 + i)N − 1) / i, where i is the monthly rate (annual ÷ 12) and N is the number of months.
How to use it
Enter what you have today, what you'll add each month, a rate you think is realistic, and how long you'll leave it. A broad global equity index has historically returned around 5–8% a year over long periods, but any single decade can be very different — try a few rates to see how much the outcome depends on it.