Investment return calculator
Project how an investment could grow over time. This is a planning tool for anyone building a portfolio, pension or savings goal — enter your inputs to see where regular investing could take you and how compounding does the heavy lifting.
How it works
The model compounds monthly. The annual return is divided by 12 to get a
monthly rate r. Starting from your lump sum, each month the balance is updated:
balance = balance × (1 + r) + monthly contribution
After the full number of years (12 × years months), it reports:
- Future value — the final balance.
- Total contributed — lump sum + all monthly contributions.
- Total growth — future value minus total contributed.
- Effective CAGR —
(future value ÷ total contributed)^(1 / years) − 1.
Example
Start with £5,000, add £300/month, assume 7% annual return over 20 years (r = 0.07 / 12 ≈ 0.00583 per month):
| Metric | Result |
|---|---|
| Total contributed | £77,000 |
| Future value | ≈ £176,000 |
| Total growth | ≈ £99,000 |
The CAGR comes out below 7% because the later contributions compounded for fewer years.
Real returns are never guaranteed — everything here is a guidance estimate calculated in your browser.