Compound Interest Calculator
See how a starting balance and regular contributions could grow over time.
How it works
The calculator simulates the account month by month: each period your balance earns interest at your annual rate divided by the compounding frequency, then your regular contribution is added. Because interest is earned on previously-earned interest, the balance grows faster than the sum of your contributions alone — that’s compounding.
Worked example
A $10,000 starting balance with $500 added each month, growing at 7% p.a. compounded monthly for 10 years:
- Amount you contribute
- $10,000 + (10 × 12 × $500) = $70,000
- Interest earned
- ≈ $36,600
- Final balance
- ≈ $106,600
Frequently asked questions
We simulate month by month: each month your balance earns interest, then your regular contribution is added — so next month's interest is earned on last month's interest too, which is what makes compounding powerful over long periods.