Savings Calculator guide
Use this calculator to project what a starting balance plus fixed monthly deposits could become over a chosen number of years. It separates the money you put in from the interest generated by the model, which makes it useful for testing a regular saving plan rather than looking only at the final balance.
The result is a scenario, not a forecast. FigureNest assumes one constant annual rate, compounds it monthly, and adds each recurring contribution at the end of the month. Real savings accounts and investments can credit interest differently and may have changing rates, fees, taxes or losses.
How the calculation works.
FV = P(1 + i)^n + C × [((1 + i)^n − 1) ÷ i]- FV = projected future balance
- P = starting balance
- C = contribution added at the end of each month
- i = entered annual rate ÷ 12 ÷ 100
- n = number of months (years × 12)
Follow the numbers in context.
$1,200 start + $300/month at 4.5% for 3 years
There are 36 month-end deposits. Deposited principal is $1,200 + (36 × $300) = $12,000. With the entered 4.5% nominal annual rate divided across monthly periods, the projected balance is about $12,912.92, so about $912.92 of the result is modeled interest.
$2,000 start + $250/month at 4% for 5 years
Deposited principal is $17,000: the $2,000 opening balance plus 60 deposits of $250. Under the calculator’s constant-rate, month-end-deposit convention, the projected balance is about $19,016.74, including about $2,016.74 of modeled interest.
Use the number for the question this tool answers.
Deposited principal is your own modeled cash input. Interest earned is the difference between the projected ending balance and that deposited principal. Keeping those figures separate shows how much of the result comes from saving versus the assumed rate.
For a near-term cash goal, contribution size can dominate the result because there is little time for compounding. Over long horizons, small changes in the assumed rate can create much larger differences, which is why comparing conservative and optimistic scenarios is more informative than relying on one projection.
More detail: inputs, assumptions, mistakes and edge cases
Build a dependable estimate.
- Enter what is already saved as the starting balance. Use zero if the plan begins with recurring deposits only.
- Enter the amount you expect to add at the end of every month, then enter an annual rate and the saving horizon in years.
- Compare deposited principal with interest earned instead of reading only the ending balance. Then test a lower rate, a higher contribution, or a shorter horizon to see which assumption matters to the plan.
Keep measurements compatible.
Money values use the selected currency denomination. Changing EUR, USD, GBP or ZAR changes labels and formatting only; FigureNest does not convert the amounts at a live exchange rate.
Enter the rate as an annual percentage, such as 4 for 4%. The calculator divides that nominal annual rate by 12 for its monthly model. This convention is not automatically equivalent to entering an account’s APY or AER, which already reflects compounding.
Know what the result includes.
Assumptions
- The annual rate remains constant for the entire horizon and is compounded monthly.
- Every recurring contribution is the same amount and arrives at the end of the month.
- Interest remains in the balance and compounds instead of being withdrawn.
- No deposits or withdrawals occur other than the starting balance and the entered monthly contribution.
Limitations
- The projection excludes taxes, account fees, inflation, withdrawal restrictions, promotional-rate expiry and changes in interest rates.
- For investments, it also excludes market volatility and sequence-of-returns risk. A smooth constant rate should not be read as a prediction of investment performance.
- The tool projects a future balance from a contribution plan; it does not solve backward for the monthly amount required to hit a target balance.
Avoid preventable errors.
- Do not treat the projected interest as guaranteed. The entered rate is an assumption that should match the scenario you actually want to test.
- Do not enter an APY or AER without recognizing the calculator’s convention: it treats the entered number as a nominal annual rate divided into 12 monthly periods.
- Do not count monthly contributions twice. Deposited principal already includes the starting balance plus every modeled monthly deposit.
- Do not compare two plans only by final balance when their contributions differ; compare how much was deposited as well as how much growth was modeled.
Check unusual inputs carefully.
At a 0% rate, there is no interest: future balance is simply starting balance + monthly contribution × number of months.
With a zero starting balance, the model grows the stream of monthly deposits alone.
With a zero monthly contribution, the calculation reduces to compound growth of the starting balance.
Beginning-of-month deposits would finish slightly higher because every contribution would receive one extra month of growth; this calculator deliberately assumes month-end deposits.
Questions about this calculation.
When does the calculator add each monthly contribution?
At the end of each month. A beginning-of-month contribution would have one additional month to compound and would produce a slightly higher result.
What happens if I enter a 0% interest rate?
The ending balance becomes the starting balance plus all monthly deposits. No interest is added.
Is the annual rate the same as APY or AER?
Not necessarily. This calculator divides the entered nominal annual rate by 12 and compounds monthly. APY or AER generally expresses an effective annual yield that already incorporates compounding.
Does changing currency convert my money?
No. Currency selection changes the denomination and formatting only. It does not use live exchange rates.
Does the result account for inflation?
No. The displayed balance is nominal. Inflation can reduce what that future amount buys, so purchasing power should be considered separately.
Can I use this as an investment return forecast?
Use it only as a mathematical scenario. Investments can rise or fall, returns vary over time, and fees and taxes can materially change actual outcomes.