Finance · Mortgages & Home Finance

Interest-Only Mortgage Repayment Plan Calculator

Project whether current savings and monthly contributions could meet an interest-only principal under two growth scenarios.

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Quick guide

How to use this calculator

  1. Enter the figures from your mortgage offer, statement, contract, property budget, or scenario.
  2. Keep currencies, rate conventions, periods, and balances consistent; compare multiple plausible scenarios where future rates or costs are uncertain.
  3. 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.