Investment Calculator

Project how an investment grows with regular monthly contributions. Enter the starting amount, contribution, years and expected return to see the future value and the growth on top of what you put in.

How it works: The starting amount and each monthly contribution grow at the annual return, compounded monthly. A steady return is assumed for illustration — real markets vary from year to year.

How the Investment Calculator Works

This calculator projects how an investment could grow when you start with a lump sum, add regular contributions, and earn a steady annual return. It is used to compare strategies — lump sum versus monthly investing, or different contribution levels — and to set realistic expectations for long-term goals such as a house deposit or retirement.

The projection uses compound growth with regular contributions. Each year, the balance grows by the assumed annual return, then the year’s contributions are added. That cycle repeats for the full period, so early contributions have the most time to compound. The calculator also splits the final value into what you contributed and what came from growth, which is often the most eye-opening part of the result.

The model assumes a constant annual return, contributions made every month, and no taxes, fees, or inflation adjustment. Real investments fluctuate, so treat the projection as a planning illustration — the value of running it is comparing scenarios on equal terms, not predicting an exact future balance.

How to Use This Calculator

Enter the initial investment — the lump sum you start with.
Enter your monthly contribution.
Enter the annual rate of return you expect.
Enter the investment period in years.
Press Calculate and compare the final value, total contributions, and investment growth.

Example

Invest $10,000 today, add $200 a month, and earn 7% a year for 20 years. The final value is $129,602.19. Your total contributions are $58,000, so $71,602.19 — more than half the final value — is growth.

Change only the monthly contribution to $400 and the final value rises to $221,358.64. Doubling the monthly input nearly doubles the growth, because every extra contribution also compounds for the rest of the period.

What Affects the Result

Monthly contribution — the most controllable lever; regular investing beats trying to time the market.
Annual return — a higher assumed return raises the projection, but higher returns come with higher risk.
Time horizon — the longer the money is invested, the more compounding dominates the result.
Initial lump sum — an early lump sum has the maximum time to grow.
Practical tip — automate the monthly contribution so it happens before you can spend the money.

The balance between lump sum and monthly contributions is worth exploring, because people often have one but not the other. Compare $50,000 invested once at 7% for 20 years — which grows to $193,484.32 — against starting from zero and contributing $250 a month at the same rate, which reaches $122,927.23. The lump sum wins here despite the monthly plan contributing $60,000 in total, because the full $50,000 compounds from day one. If you come into a windfall — a bonus, an inheritance, a property sale — investing it sooner rather than dripping it in slowly usually wins on the maths, provided you can tolerate the market swings. Monthly contributions, though, are how most people actually build wealth, and their strength is consistency through every market mood.

One more factor the model leaves out deserves a mention: fees and taxes quietly take a share of the growth the projection shows. An annual fund fee of 1% does not sound like much, but over 20 years it can reduce a final value by roughly a fifth compared with a no-fee equivalent, because the fee compounds against you just as returns compound for you. Taxes on gains work the same way. When you compare real products, run this calculator with a return net of fees — if a fund promises 7% but charges 1%, model it at 6% — and you will get a far more honest picture of what you are likely to keep.

Investment Calculator FAQs

What return should I expect?

It depends on the investment. Broad stock market investments have historically averaged around 7–10% a year over long periods before inflation, but with large ups and downs along the way. Lower-risk options return less. Use a conservative estimate for planning.

Is it better to invest a lump sum or monthly?

Mathematically, a lump sum invested early usually wins because it has more time to compound. But monthly investing is more practical for most people and smooths out market ups and downs. The best approach is often both: invest what you have now, then keep adding monthly.

Does this calculator account for inflation?

No — the projection is in nominal terms. Over long periods, inflation reduces what the final figure will buy, so keep that in mind when judging the result.

What about taxes and fees?

The calculator does not deduct them. In real life, fees reduce returns and taxes may apply to gains. Model a slightly lower return to approximate their effect.

Can I use this for retirement planning?

Yes — this calculator works well for retirement projections, and the retirement calculator adds age-based framing around the same idea. Use both to cross-check your plan.