Investment simulator

How it works

Each month: value = value × (1 + monthly rate) + contribution, monthly rate = (1 + annual return − fees)^(1/12) − 1

Contributions are added at the end of each month, which is the conservative convention and the one that matches a standing order. Fees come off the return before it compounds — a 0.5% annual fee against a 7% return means the money grows at 6.5%, every year, which over twenty years is a much larger hole than it looks. Inflation is applied to the result, not the return, so the real value line answers 'what will this buy' rather than 'what will the statement say'.

This tool runs entirely in your browser. Nothing you type is sent to a server, stored or logged.

Frequently asked questions

Is this a prediction?

No. It compounds the rate you type at a steady pace. Real markets do not move steadily, and a bad first decade produces a very different outcome from the same average return arriving later.

Why is the real value so much lower?

That is inflation doing what it does. At 2% a year, money loses about a fifth of its purchasing power over a decade — the nominal figure is not wrong, it just answers a different question.

Where do fees fit in?

They are subtracted from the annual return before compounding, which is how a fund's ongoing charge actually works. It is the single input people most often leave at zero and most regret.

Are contributions at the start or end of the month?

The end. Contributing at the start would earn one extra month of return on every payment and produce a slightly higher, slightly optimistic number.