Interest Growth Calculator
Project your investment growth over time with compound interest, regular monthly deposits, and inflation adjustment projections.
Also covers: compound interest calculator with monthly contributions and inflation · investment return projection · compound annual growth
Formula & How It Works
A = P(1 + r/n)^(nt) + contributions each period
- P is the starting deposit, r the annual rate as a decimal, n the compounding periods per year, and t the number of years.
- Deposits are added once per compounding period — at the end of it by default, or at the start if you choose “beginning”, which gives every deposit an extra period of growth.
- The balance is compounded period by period, so interest is earned on interest as well as on your own deposits.
Step-by-Step Example
$10,000 to start, $250 added every month, 6% annual rate, monthly compounding, contributions at the end of each month, over 10 years.
- 1.Starting principal (P)
- $10,000
- 2.Rate per period
- 6% ÷ 12 = 0.5% a month
- 3.Your deposits over 10 years
- $250 × 120 = $30,000
- 4.Compounding
- balance grows 0.5%, then the $250 is added
$59,164 after 10 years — $40,000 of that is your own money and $19,164 is compound interest.
Frequently asked questions
How often does compound interest compound on typical savings?
High-yield savings accounts usually compound daily or monthly and credit the interest monthly, and most certificates of deposit compound daily or monthly as well. This calculator offers daily, monthly, and annual compounding so you can match your account. For the same nominal rate, more frequent compounding produces a higher effective annual yield.
How does inflation affect long-term compound interest returns?
Inflation does not change the balance, it changes what the balance can buy. A 6% return with 3% inflation is roughly a 3% real return, so purchasing power grows more slowly than the headline figure suggests. Subtracting expected inflation from the return is the quick estimate; this page models nominal growth only, so note that the ending balance is before inflation.
What is the mathematical formula for compound interest?
For a lump sum it is A = P(1 + r/n)^(nt), where P is the principal, r the annual rate as a decimal, n the periods per year, and t the number of years. Regular contributions add a separate term for each deposit, which is why this calculator accumulates the balance and the deposits period by period instead of using the single lump-sum formula.
About the Interest Growth Calculator
Project your investment growth over time with compound interest, regular monthly deposits, and inflation adjustment projections.
It runs entirely in your browser — nothing you type is sent to a server — and the result updates as you edit the inputs. Estimates are for educational and informational purposes only; see ourdisclaimer.
Common searches
- interest
- savings
- apc
- growth
- future value
Related calculators
Browse more inFinancial.