Set a starting pot, a monthly amount and a return. Watch compounding do the heavy lifting, the number updates live.
Each month your pot earns a slice of the annual return, then the new total earns a return next month, that's compounding. Future value ≈ starting pot grown for the period + every monthly payment grown from the date you made it. The longer the time, the more of the final pot is growth rather than the cash you put in.
Example: £200/month for 30 years at 5% after inflation grows to about £166,000 yet you only paid in £72,000. The other ~£94,000 is compound growth. Start ten years earlier and the same £200 lands far higher: time beats amount.
A 5% real return is a common long-run assumption for a global equity fund (~7% before inflation). Returns are not guaranteed; markets fall as well as rise. Inside an ISA this growth is tax-free (£20,000/yr allowance in 2026/27).
Illustrative only, not financial advice. This models steady monthly contributions compounding at a constant annual return; real returns vary year to year, and fees, tax and inflation all affect the outcome. Your capital is at risk, investments can fall as well as rise. Figures use the 2026/27 tax year. Always do your own research or speak to a qualified adviser.
See also the 2026/27 tax rates.