Tools
Financial calculators
Most online calculators hide their assumptions, which makes the output impossible to check. These four state every formula and every simplification, so you can see exactly what each number does and does not account for.
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Four educational tools · Reviewed
Compound growth projection
See how an initial balance and regular contributions could grow, and how much of the final figure comes from your own deposits rather than returns.
Hypothetical constant annual rate, not a market forecast or recommended assumption.
Illustrative balance
$352,656
- Total you contribute
- $125,000
- Growth on contributions
- $227,656
- Growth share of balance
- 65%
How this is calculated
- Monthly compounding is applied to the starting balance and to each contribution as an ordinary annuity (deposits at period end).
- The return rate is assumed to be constant. Real markets are not — actual sequences of returns vary widely and can materially change the outcome.
- Figures are nominal. They ignore inflation, taxes, fund fees and trading costs, all of which reduce the amount you keep.
Debt payoff and extra-payment impact
Work out how long a balance takes to clear at your current payment, what the interest costs, and how much both change if you add a fixed amount each month.
Must exceed the first month's interest or the balance will never fall.
Payoff at current payment
6 yr 5 mo
- Total interest paid
- $16,306.32
- Total amount repaid
- $34,306.32
Adding $100.00 a month
4 yr 4 mo
- Interest saved
- $5,803.49
- Months sooner
- 25
How this is calculated
- This simplified model accrues interest monthly, then applies a payment. Actual loans may use daily interest, different posting dates and additional fees.
- The rate is held constant. Variable-rate balances such as most credit cards can reprice, which changes the schedule.
- New spending on the account is assumed to be zero. Continuing to charge the card is the most common reason a real payoff takes longer than projected.
Emergency-fund scenario
Choose a period of expenses and see the arithmetic. The tool does not determine an appropriate reserve for your circumstances.
Amount for this scenario
$6,000
- Gap from starting reserve
- $5,000
- Time under these assumptions
- 20 months
How this is calculated
- Scenario amount = monthly expenses × selected months + additional costs.
- Months to close the gap assumes constant contributions, no interest and no withdrawals.
- The selected period is your assumption, not a professional recommendation or guarantee of adequate protection.
Future purchasing power
Estimate what a fixed amount of money could buy in the future if prices rise at a constant illustrative rate.
A hypothetical constant rate, not a prediction.
Purchasing power after 20 years
$61,027
- Starting amount
- $100,000
- Illustrative buying-power reduction
- $38,973
- Future cost of today's $100,000
- $163,862
How this is calculated
- Purchasing power divides the amount by (1 + inflation rate) raised to the number of years.
- The inflation rate is held constant for the entire period. Actual inflation changes over time and differs by product, service and location.
- This model does not forecast inflation or account for investment returns, taxes, income growth or changes in spending patterns.
Read the reasoning behind the maths
A projection is only useful if you understand the mechanism it models. These courses explain what drives each calculation.
These calculators are educational models, not financial advice or a prediction of your results. They use simplifying assumptions stated under each tool and exclude taxes, fees and inflation unless noted. Verify any figure that informs a real decision with a licensed professional.