Use this when…
- You are saving toward a down payment, education or a future purchase.
- You want to compare saving $100 versus $300 a month.
- You want to understand why growth, fees and inflation produce different figures.
US · COMPOUND INTEREST & SAVINGS
See what compounding could do for your savings
Plan a long-term savings or investment scenario with your own return assumption. Compare invested dollars, possible gains, inflation-adjusted value and the monthly amount needed to reach a goal.
NEW TO THIS CALCULATOR?
Compound interest: see how small monthly saving can add up
Use this when you want to see what might happen if you start with some savings and add money regularly. You do not need to know investment formulas: begin with the dollars you already have, the amount you can add each month and a time period.
Start with these numbers
- 1. Type the amount already saved and how much you could actually contribute monthly.
- 2. Choose the number of years and an assumed yearly return. Put 0% first to see the contributions alone.
- 3. Optional: enter yearly fees, annual increases to saving, inflation and your target amount.
What the result means
'Total deposited' is money you put in. 'Projected future balance' adds hypothetical investment growth or loss. 'Today's purchasing power' adjusts the balance for assumed inflation; the target result is not a promise.
Try this example
Start at $10,000, add $500 monthly for 20 years. Compare 0% and 6% assumed return while keeping fees at 0%. Use the year-by-year table to see how later years differ.
Watch out for this mistake The return field is not a live bank interest quote. Do not enter a fund fee again when the performance assumption already subtracts it.
More detailed explanations appear below the calculator ↓
Your saving assumptions
This is an education and planning model, not an investment recommendation or a product yield quote. Assumes a constant effective annual return and expense drag, with monthly compounding and deposits. Market returns vary and investments can lose value; taxes, trading fees, cash flows, contribution limits and withdrawal restrictions are not included.
Your projection
Projected future balance$258,790.67Goal achieved in this illustration
Your future investment value
Total deposited including starting amount$130,000.00
Investment gain or loss$128,790.67
Value in today's purchasing power$174,158.70
Monthly amount to reach goal$370.34
Net annual return after fee assumption6%
What if the growth rate changes?
Lower scenario (4%)$203,832.10
Your assumption (6%)$258,790.67
Higher scenario (8%)$331,109.11
Year-by-year projection
| Year | Deposited | Projected balance |
|---|---|---|
| 0 | $10,000.00 | $10,000.00 |
| 1 | $16,000.00 | $16,763.26 |
| 5 | $40,000.00 | $48,125.15 |
| 10 | $70,000.00 | $99,145.20 |
| 15 | $100,000.00 | $167,421.53 |
| 20 | $130,000.00 | $258,790.67 |
FINANCIAL EDUCATION
How to use this compound interest calculator
- 01
Enter your existing savings and the amount you plan to contribute each month. Set monthly deposits to zero to model a lump-sum investment only.
- 02
Enter the investment horizon and an assumed effective annual return. This is not a bank APY quotation, guaranteed stock return or prediction of market performance.
- 03
If relevant, add estimated annual asset-based fees, yearly increases to your monthly deposit and inflation. Choose whether money goes in at the start or end of each month.
- 04
Enter a target future balance to calculate the starting monthly contribution you would need under exactly the same assumptions. Review the year-by-year projection and try lower returns to test your plan.
Example: $10,000 starting savings plus $500 at each month-end for 20 years. Adjust the assumed return from 0% to 6% and compare how much of the ending balance comes from deposits versus hypothetical investment growth.
What this model cannot predict
This is an education and planning model, not an investment recommendation or a product yield quote. Assumes a constant effective annual return and expense drag, with monthly compounding and deposits. Market returns vary and investments can lose value; taxes, trading fees, cash flows, contribution limits and withdrawal restrictions are not included.
Frequently asked questions
Does the calculator use bank APR or APY?
It treats the entered growth percentage as an effective annual rate, similar in structure to APY. APR with a different compounding schedule may produce a different result.
Are 401(k) taxes and IRS contribution limits included?
No. The scenario ignores tax on returns and retirement-account contribution limits. Use account-specific and tax-year rules separately.
Does a 4% inflation assumption reduce my balance?
No. It changes the displayed purchasing-power equivalent, not the nominal amount shown in the account.
Is my monthly goal contribution guaranteed to work?
No. It is algebraically derived under the same constant return, fee and deposit-growth assumptions, which real investments cannot guarantee.
How the monthly calculation works
The growth engine converts an assumed effective annual rate to a monthly multiplier. Asset-based fees apply each month; deposits follow the timing you select. Every twelve months, the monthly contribution can step up. These are mathematical scenarios, not live yields.
What if the growth rate changes?
IN-DEPTH CALCULATOR GUIDE
Compound interest: see how small monthly saving can add up
Use this when you want to see what might happen if you start with some savings and add money regularly. You do not need to know investment formulas: begin with the dollars you already have, the amount you can add each month and a time period.
01
When do people need a compound interest calculator?
People use compounding estimates to compare saving for a home deposit, retirement, college costs or another long-term goal. A small regular deposit can become a substantial sum over many years, even without assuming investment gains; the calculator makes that distinction visible.
Compounding means previously earned growth may itself affect later growth. This is a mathematical pattern, not a guarantee. Actual savings accounts have product terms and investment portfolios can lose money.
02
Start with the money you control
Enter your present balance and the monthly amount you can realistically spare. If you have no money saved, enter zero at the start. If you only want to test a lump sum, enter zero monthly. Select a whole number of years for your proposed horizon.
Set the assumed annual return to 0% first to find a clear deposits-only baseline. Then test another scenario, such as 4% or 6%, without assuming it is a rate any bank or stock fund currently offers.
03
What is the difference between contributed and projected money?
The total deposited line is your opening money plus all modelled deposits. The projected future balance includes growth or losses under your assumed rate and fees. Their difference is a hypothetical investment result, not cash already received.
An inflation-adjusted line translates the future balance into today's purchasing power. Inflation doesn't remove dollars from your account but can make the same balance buy fewer goods. Watch the year-by-year table instead of judging only the ending number.
04
Fees, step-ups and saving goals explained
A yearly deposit increase means the monthly saving amount rises after every twelve months, useful if you expect salary increases. The yearly asset fee is a recurring percentage drag, not a tax estimate. If return assumptions are already after costs, another fee deduction could count charges twice.
A savings target produces a required starting monthly contribution under the same model. This is a calculation of 'what would I need if these assumptions held', not proof the target can be achieved. Use several return scenarios and compare with real product disclosures.
Educational planning only. Verify relevant official records and lender or tax documents before making decisions.