What the Part Repayment, Part Interest-Only Mortgage Calculator is for
Split one mortgage between amortizing and interest-only portions and expose the end-of-term principal still due.
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
Combined payment = level payment on repayment portion + monthly interest on interest-only portion.
Visual explanation
See which inputs change the result
Stage 1→Stage 2→Later stageRecalculate from the balance remaining at each changeCombined payment = level payment on repayment portion + monthly interest on interest-only portion.
Read the estimate correctly
Use the result with its assumptions
Split a 300,000 mortgage into 200,000 repayment and 100,000 interest-only.
A credible plan is required for the interest-only principal. This calculator does not judge repayment vehicles or product suitability.
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
Combined payment = level payment on repayment portion + monthly interest on interest-only portion.
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
Split a 300,000 mortgage into 200,000 repayment and 100,000 interest-only.
Combined payment = level payment on repayment portion + monthly interest on interest-only portion.
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
A credible plan is required for the interest-only principal. This calculator does not judge repayment vehicles or product suitability.
