Interest Calculator
Calculate investment growth with annual and monthly additions, taxes, and inflation.
Project the balance, contributions, and earnings over time.
Result
- Contributions
- Net earnings
The ending balance includes $22,000.00 of your own money (starting amount plus deposits). Net investment earnings are $9,998.32, after the entered tax on interest. These are modeled amounts, not guaranteed returns.
Interest is accrued monthly using the selected compounding equivalent. Tax is charged on positive interest at each year end; tax losses are not carried forward.
Calculation details
Scroll horizontally or vertically to see more. Download CSV for the complete schedule.
| Month | Contributions | Net earnings | Balance |
|---|---|---|---|
| 1 | 10,100 | 41.67 | 10,141.67 |
| 2 | 10,200 | 83.92 | 10,283.92 |
| 3 | 10,300 | 126.77 | 10,426.77 |
| 4 | 10,400 | 170.22 | 10,570.22 |
| 5 | 10,500 | 214.26 | 10,714.26 |
| 6 | 10,600 | 258.90 | 10,858.90 |
| 7 | 10,700 | 304.15 | 11,004.15 |
| 8 | 10,800 | 350.00 | 11,150.00 |
| 9 | 10,900 | 396.46 | 11,296.46 |
| 10 | 11,000 | 443.53 | 11,443.53 |
| 11 | 11,100 | 491.21 | 11,591.21 |
| 12 | 11,200 | 539.50 | 11,739.50 |
| 13 | 11,300 | 588.42 | 11,888.42 |
| 14 | 11,400 | 637.95 | 12,037.95 |
| 15 | 11,500 | 688.11 | 12,188.11 |
| 16 | 11,600 | 738.90 | 12,338.90 |
| 17 | 11,700 | 790.31 | 12,490.31 |
| 18 | 11,800 | 842.35 | 12,642.35 |
| 19 | 11,900 | 895.03 | 12,795.03 |
| 20 | 12,000 | 948.34 | 12,948.34 |
| 21 | 12,100 | 1,002.29 | 13,102.29 |
| 22 | 12,200 | 1,056.88 | 13,256.88 |
| 23 | 12,300 | 1,112.12 | 13,412.12 |
| 24 | 12,400 | 1,168.01 | 13,568.01 |
| 25 | 12,500 | 1,224.54 | 13,724.54 |
| 26 | 12,600 | 1,281.72 | 13,881.72 |
| 27 | 12,700 | 1,339.56 | 14,039.56 |
| 28 | 12,800 | 1,398.06 | 14,198.06 |
| 29 | 12,900 | 1,457.22 | 14,357.22 |
| 30 | 13,000 | 1,517.04 | 14,517.04 |
| 31 | 13,100 | 1,577.53 | 14,677.53 |
| 32 | 13,200 | 1,638.69 | 14,838.69 |
| 33 | 13,300 | 1,700.52 | 15,000.52 |
| 34 | 13,400 | 1,763.02 | 15,163.02 |
| 35 | 13,500 | 1,826.20 | 15,326.20 |
| 36 | 13,600 | 1,890.06 | 15,490.06 |
How to use this calculator
Project the balance, contributions, and earnings over time. Enter amounts in the units shown, select the applicable options, and click Calculate. Use Reset to restore the starting values.
Calculation formula
Balance grows at the equivalent periodic rate, with contributions added at the selected timing.
Assumptions and accuracy
Review timing, rates, fees and result notes when comparing scenarios. Future returns and rates are assumptions rather than guaranteed outcomes. Monetary display follows the currency’s precision; intermediate calculations retain additional digits.
Choose what to calculate
Interest calculator with regular contributions
Project interest from starting savings and recurring contributions, with selected compounding, deposit timing, tax and inflation assumptions.
Open this calculationUnderstanding this calculation
Compound growth earns interest on both the original amount and accumulated interest. Contribution timing, compounding frequency, tax and inflation can change the projected ending balance.
Worked examples
Grow 1,000 at 5% with no additions
Starting amount $1,000; 5% annually compounded; 10 years; no deposits, taxes or inflation.
- Growth factor = 1.05^10.
- Ending balance = 1000 × 1.05^10 = 1628.8946…
The ending balance is $1,628.89; earnings are $628.89.
Try these inputsCommon questions
Are nominal and effective annual rates the same?
They coincide with annual compounding. With more frequent compounding, a nominal annual rate generally produces a different effective annual yield.
Do contributions at the beginning earn more interest?
At a positive return, a beginning-of-period contribution earns one more period of interest than the same contribution at period end.
Scope and assumptions
Returns are assumed constant. Positive interest is taxed using the entered planning rate; historical volatility, investment-specific tax rules and transaction fees are not inferred.
Sources
Calculation notes checked . Examples are mathematical checks under the stated assumptions.
Calculation methods and formulas
Interest Calculator
Project the balance, contributions, and earnings over time.
Balance grows at the equivalent periodic rate, with contributions added at the selected timing.
See our calculation methodology and review status for data versions, rounding and validation limitations.