Model investment growth with your starting balance, monthly contributions, one-off lump sums, a custom rate of return, and optional inflation adjustment — with a full year-by-year breakdown.
Currency
Inputs
Lump sum deposits
Model a bonus, inheritance, or property sale proceeds at a future year.
Value in 20 yrs
£300,851
Total invested
£130,000
Total interest earned
£170,851
Interest / invested ratio
131%
Growth breakdown at year 20
7% annual return, compounded monthly
This calculator uses a fixed annual rate of return compounded monthly. It does not model market volatility, taxes, or fees. Results are for illustrative purposes only and do not constitute financial advice. Past performance does not guarantee future returns.
Compounding means your returns earn returns. A £10,000 investment at 7% earns £700 in year one. In year two it earns 7% on £10,700 — that extra £49 is compounding in action. Over decades, this effect becomes extraordinary: the same £10,000 with no additional contributions becomes £76,000 after 30 years at 7%. Add £500/month and it grows to over £620,000.
A nominal return of 7% sounds great. But if inflation runs at 2.5%, your real purchasing power grows at roughly 4.5%. Enabling inflation adjustment in the calculator shows you what your projected balance is actually worth in today's money — a more honest picture of your future wealth.
Inheritances, bonuses, property sale proceeds — large one-off amounts deposited at a specific point in time can dramatically reshape your trajectory. The lump sum section lets you model up to several of these at precise year intervals so you can see their compounded effect.
This calculator uses a fixed rate of return. Our Portfolio Projections tool runs 1,000 simulated futures using historical volatility per asset class — showing the realistic cone of outcomes rather than a single optimistic line.