Finance & Business
Investment Calculator
Calculate the potential growth of your investments over time, including initial investments, regular contributions, and expected returns.
Reviewed by the calculator.uk.com Team · Last reviewed 30 May 2026 · Our methodology
Enter your investment details to see projected returns
The Investment Calculator uses compound interest principles to project the potential growth of your investments over time. It takes into account your initial investment, regular monthly contributions, expected annual return rate, and investment period to calculate how your money could grow.
Compound Interest Formula
The calculator uses monthly compounding to provide more accurate results. For each month, it calculates the interest earned on both your initial investment and previous earnings, plus any additional monthly contributions. This compounding effect can significantly increase your investment's growth over time.
The calculation considers three main components: your initial investment, regular monthly contributions, and the compound interest earned on both. The annual return rate is converted to a monthly rate, and interest is calculated and compounded monthly to reflect real-world investment scenarios more accurately.
The calculator provides a comprehensive view of your investment's potential growth through several key metrics and a visual graph. Understanding these results helps you make informed investment decisions and track your progress toward financial goals.
Key Metrics Explained
Total Investment Value: The final value of your investment, including your initial investment, all contributions, and earned returns.
Total Contributions: The sum of your initial investment and all monthly contributions over the investment period.
Total Return: The profit earned from your investments, calculated as the difference between the total investment value and total contributions.
The interactive graph shows the growth of your investment over time, with separate lines for total balance, contributions, and returns. This visual representation helps you understand how compound interest and regular contributions affect your investment's growth trajectory.
1. How does compound interest affect investment growth?
Compound interest means you earn returns not only on your initial investment and contributions but also on previously earned returns. This creates an exponential growth effect that becomes more powerful over longer investment periods, potentially leading to significantly higher returns compared to simple interest.
2. Why do monthly contributions matter?
Regular monthly contributions help accelerate your investment growth by consistently adding to your investment base. Each contribution starts earning compound returns immediately, and over time, these regular additions can significantly impact your total investment value.
3. How realistic is the expected annual return rate?
Historical stock market returns have averaged around 7-10% annually over long periods, but actual returns can vary significantly. It's important to use conservative estimates and understand that past performance doesn't guarantee future results. Consider consulting with a financial advisor to set realistic expectations based on your investment strategy.
4. Should I increase my monthly contributions over time?
Increasing your monthly contributions over time can help accelerate your investment growth and potentially help offset inflation. Consider reviewing and adjusting your contribution amount annually based on changes in your income, expenses, and financial goals.
5. What is the scientific source for this calculator?
This calculator combines the compound interest formula with the future value of an annuity formula to project how a lump sum plus regular contributions grows over time, standard time-value-of-money mathematics covered in corporate finance texts such as Brealey, Myers and Allen's. The same combined formula underlies most retirement and savings projections used by financial institutions and advisers.