Compound growth
What regular saving could grow into over time, and how much of the final pot is growth rather than your own contributions.
Each month the pot grows by a twelfth of the annual rate, then the new contribution is added.
Each month the pot grows by a twelfth of the annual rate, then the new contribution is added. Growth earned in early years earns its own growth in later years — the effect is small at first and dominant by the end.
The grey line shows contributions alone. The gap between the lines is compounding; it widens fastest in the final third of the period, which is why starting early matters more than contributing more.
Formula
FV = P(1+r)ⁿ + c · ((1+r)ⁿ − 1) ⁄ r
where P is the starting amount, c the monthly contribution, r the monthly rate and n the number of months.
- 01Compounds monthly; contributions added at the end of each month.
- 02Returns are assumed smooth. Real returns are not, and the order of good and bad years matters.
- 03No allowance for charges, tax or inflation. Figures are nominal pounds.
- 04Contributions are held constant; in reality most people increase them over time.
Holding everything else at your inputs
Each row changes one variable and shows the result. It illustrates which assumptions the answer is most sensitive to — it does not suggest which to choose.
| Variable | Changed to | Final pot | vs your result |
|---|
Reminder: this tool is general education. It doesn't know your circumstances and isn't a personal recommendation. For decisions, consult an FCA-authorised adviser — our toolkit shows how to find one.