What the Interest-Only Mortgage Repayment Plan Calculator is for
Project whether current savings and monthly contributions could meet an interest-only principal under two growth scenarios.
It keeps the property value, balance, cash amounts, rate convention, payment timing, and comparison horizon visible so the result can be checked against an actual quote, statement, budget, or contract.
Calculation structure
Follow the money through time
Future value = current plan value compounded monthly + end-of-month contribution annuity value.
Visual explanation
See which inputs change the result
Stage 1→Stage 2→Later stageRecalculate from the balance remaining at each changeFuture value = current plan value compounded monthly + end-of-month contribution annuity value.
Read the estimate correctly
Use the result with its assumptions
Project a repayment plan for a 150,000 principal with 20 years remaining under 2% and 5% growth.
Growth can be negative in reality, fees and tax may apply, and investment values can fall. This does not determine whether a lender accepts a repayment vehicle.
Quick guide
How to use this calculator
Enter the figures from your mortgage offer, statement, contract, property budget, or scenario.
Keep currencies, rate conventions, periods, and balances consistent; compare multiple plausible scenarios where future rates or costs are uncertain.
Use the component outputs to verify the result and review the calculator-specific boundary before acting.
Calculation method
Calculation method
Future value = current plan value compounded monthly + end-of-month contribution annuity value.
Mortgage schedules use stable level-payment arithmetic and advance only the explicitly entered scenario. Results are checked for finite, principal-reducing behavior and round only for display.
Worked example
Practical example
Project a repayment plan for a 150,000 principal with 20 years remaining under 2% and 5% growth.
Future value = current plan value compounded monthly + end-of-month contribution annuity value.
Supported inputs
Precision and limits
Visible input limits
Amounts are capped at 1e12, rates at 1000% unless a narrower percentage applies, and schedules at 1,200 months unless a frequency comparison explicitly documents more payment periods.
International scope
No currency, country, tax system, mortgage program, lender threshold, insurance rule, market rate, escrow law, or contract term is assumed.
Decision boundary
These are arithmetic scenarios, not offers, approvals, regulated disclosures, forecasts, valuations, legal interpretations, hardship advice, or recommendations.
Calculator-specific assumptions
Growth can be negative in reality, fees and tax may apply, and investment values can fall. This does not determine whether a lender accepts a repayment vehicle.
