A familiar situation
A regular deposit can make a long-term savings projection look quite different from a one-time investment. Vary monthly contributions and the assumed return to see how compounding and new deposits each affect the balance.
How to use this calculator
- Enter starting balance, contribution per month, assumed annual return and the remaining inputs.
- Select Calculate to see the answer and its breakdown.
- Keep a scenario, change an input and compare the results.
Use consistent units and check the assumptions below before applying the result.
How compound interest is calculated
The projection compounds the opening balance monthly and treats each regular contribution as arriving at month end. It is a scenario with a steady return, not a forecast of market performance. Formula: Balance = starting principal compounded monthly + contributions compounded monthly. Use the displayed details to inspect the intermediate amounts and replace example assumptions with terms from your own quote or records.
Balance = starting principal compounded monthly + contributions compounded monthly.A $1,000 start plus $100 monthly at 5% for 10 years grows to roughly $16,900.
Assumptions & useful context
Constant monthly compounding is illustrative; returns vary and the estimate is before taxes, fees and inflation.
Financial projections use your assumptions. Actual returns, lender terms, fees and tax rules can differ; these results do not guarantee a future outcome.
Frequently asked questions
Compound Interest Calculator: what does the result include?
Each contribution is added at the end of the month, so it earns interest only in later periods. Deposits at the beginning of a month would produce a slightly higher estimate.
Compound Interest Calculator: which assumptions matter most?
No. It repeats one annual rate to illustrate compounding; actual returns vary and fees, taxes and inflation reduce spending power.