Savings & interest
Compound interest with contributions
Calculate savings growth with regular monthly deposits, selectable deposit timing, and effective annual or nominal compounded interest.
Your inputs
Complete the fields for your selected method. Zero means intentionally zero, not unknown. Currency selection labels amounts; it does not convert exchange rates.
How this calculation works
future balance = initial × monthly growth factor^months + monthly contributions × stated accumulation factor
A constant-rate arithmetic scenario, not a forecast or promised return. Supply your own return assumptions; example rates are not recommended investments. Monthly contributions are fixed nominal amounts, not automatically increased for inflation. No taxes, contribution limits, account eligibility, trading costs or benefits are inferred. Negative returns are supported; actual return sequences can differ materially. For products that credit interest using daily transaction dates or impose deposit restrictions, use their actual terms. This is not a quoted bank yield.
What information do I need?
Use records for the same job, equipment or accounting period. Only the fields for your selected entry method are required. An unknown amount is not zero.
Input definitions and where to find them
- Starting savings or investment balance (selected currency): The balance already available at the start, not future contributions.
- Monthly contribution (selected currency): A fixed amount added each month on the selected timing. Do not count the same contribution twice.
- Projection length entry: Use matching records or a clearly stated assumption for the indicated period. Prefilled figures are illustrative. An unknown value is not zero.
- Years to project (years): Use matching records or a clearly stated assumption for the indicated period. Prefilled figures are illustrative. An unknown value is not zero. Used with: Whole years.
- Months to project (months): Use matching records or a clearly stated assumption for the indicated period. Prefilled figures are illustrative. An unknown value is not zero. Used with: Whole months.
- How is your assumed annual growth rate stated?: Use matching records or a clearly stated assumption for the indicated period. Prefilled figures are illustrative. An unknown value is not zero.
- Your assumed annual growth rate (%): Supply an assumed annual rate on the selected basis. Use effective annual growth or APY unless you specifically have a nominal rate and compounding frequency. The example is not a current quote or forecast.
- Compounding frequency for nominal rate: Use matching records or a clearly stated assumption for the indicated period. Prefilled figures are illustrative. An unknown value is not zero. Used with: Nominal annual rate with stated compounding.
- When is each monthly contribution added?: Use matching records or a clearly stated assumption for the indicated period. Prefilled figures are illustrative. An unknown value is not zero.
Use the Where to find this value controls beside the inputs for available work-it-out helpers. Estimates remain your assumptions; a helper does not verify the source figures.
Worked example
Example amounts use US dollars (USD).
Example answer: Projected ending balance is $17,065.21 for the illustrative inputs below.
Example inputs
- Starting savings or investment balance: $1,000.00
- Monthly contribution: $100.00
- Projection length entry: Whole years
- Years to project: 10 years
- How is your assumed annual growth rate stated?: Effective annual return or APY
- Your assumed annual growth rate: 5.00 %
- When is each monthly contribution added?: End of month
- Projected ending balance
- $17,065.21
- Starting amount plus contributions
- $13,000.00
- Modeled interest or investment growth
- $4,065.21
- Effective annual growth rate used
- 5.00000 %
- Monthly contributions modeled
- 120 months
- A nominal rate is converted using its selected compounding frequency; monthly deposits use an equivalent monthly accumulation rate.
- ━ Balance
- ┄ Money contributed
These illustrative values are not recommended rates or industry averages. Replace every example input with your own figures.
Use the result well
Calculate savings growth with regular monthly deposits, selectable deposit timing, and effective annual or nominal compounded interest.
Keep inputs on the same scope and time basis. Calculations retain precision internally; displayed values generally round to two decimal places, with extra precision for very small values and whole-unit rounding where required. Economic comparisons describe your supplied assumptions and do not guarantee future results.
This tool provides business arithmetic. It does not approve engineering designs, establish legal or tax treatment, select equipment or certify safe operating conditions.