Quick answers to common questions about compound interest, savings goals, mortgages, FIRE planning, and how to get the most from these calculators.
Compound interest means you earn returns not only on your original contributions, but also on the growth that has already been added over time. In practice, this is why starting early and contributing regularly can make a big difference over long periods.
The compound interest calculator lets you choose a compounding frequency (for example monthly or annually). The projections use that frequency together with your annual rate to estimate how balances evolve over time.
Use the Compound Interest Calculator to model different contribution amounts, rates, and time horizons.
A common approach is to start from a target amount and timeframe, pick a reasonable long-term return assumption, and then solve for the monthly contribution that gets you close to that target.
The default 7% is a planning assumption for long-term real returns after inflation. It is not a promise. The calculator is designed for testing different assumptions rather than predicting an exact outcome.
Use the Savings Goal Calculator to work backwards from a target amount and timeline to a monthly saving figure.
Most repayment mortgages use an amortization formula. Each monthly payment covers that month’s interest plus some repayment of the loan principal so the balance falls over time.
Loan-to-value is the loan amount divided by the property value. A lower LTV usually means lower risk for the lender and can unlock better rates, but every lender has its own criteria.
Use the House Deposit & Mortgage Calculator to explore different house prices, deposit sizes, rates, and terms.
A FIRE number is a planning estimate for the portfolio size that could support your annual spending through withdrawals, often based on a chosen withdrawal rate such as 4%.
No. The 4% rule is a simplifying rule of thumb based on historical data, not a promise for every future market path. Real outcomes depend on returns, inflation, tax, fees, and how flexible your spending can be.
Use the FIRE Calculator to project your portfolio towards a FIRE target and see a rough timeline based on your savings and return assumptions.
No. The calculators are educational tools to help you explore scenarios and trade-offs. They do not account for your full situation and should not be treated as regulated financial advice.
If you are new to investing, the Compound Interest Calculator is a good starting point for understanding how regular contributions and time affect outcomes. From there you can explore savings goals, mortgages, or FIRE planning.