Estimate Your Savings Growth
Assumes a constant annual rate divided by 12, monthly compounding, and contributions at the end of each month. Taxes, fees, and inflation are excluded. Actual returns may vary.
How Compound Interest Works
Compound interest adds interest to your balance, so future interest is calculated on both your contributions and previously earned interest.
Each month's ending balance = Previous balance × (1 + Annual rate ÷ 100 ÷ 12) + Monthly contribution
The calculator repeats this step for each month. Total contributions include the starting balance and all monthly deposits. Interest earned is the projected balance minus those contributions.
Example: $1,000 to Start, Plus $100 a Month
Using an illustrative 5% annual rate for 10 years:
Projected balance: $17,175.24
Total contributions: $13,000.00
Interest earned: $4,175.24
These figures assume 120 end-of-month contributions and monthly compounding. The 5% rate is an example, not a predicted return.
Common Compound Interest Questions
Can I calculate growth without monthly deposits?
Yes. Set the monthly contribution to 0 to project growth on just your starting balance.
What happens at a 0% interest rate?
The ending balance equals your starting balance plus your monthly contributions. No interest is added.
When are contributions added?
After interest is calculated at the end of each month. Deposits made at the beginning of a month would have more time to earn interest.
What rate does this calculator use?
It uses the annual rate you enter divided by 12 as the monthly rate. It does not treat the entered value as an effective annual yield or look up current rates.
Can I enter a partial year?
Yes, provided it equals a whole number of months. For example, 0.5 years equals 6 months. At zero years, the result is your starting balance.
How are amounts rounded?
The calculation keeps unrounded balances between months and displays results to the nearest cent.