What the Mortgage Porting and Additional Borrowing Calculator is for
Combine the payment impact of a ported mortgage part and new borrowing while preserving their separate rates and terms.
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 = payment on ported balance + payment on additional balance and entered financed fees.
Visual explanation
See which inputs change the result
Opening balanceinterest+principalScheduled paymentBalance declines across the entered termCombined payment = payment on ported balance + payment on additional balance and entered financed fees.
Read the estimate correctly
Use the result with its assumptions
Port 180,000 at 3% and add 70,000 at 6%.
Porting is normally a new application and depends on lender approval, property, timing, and contract terms.
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 = payment on ported balance + payment on additional balance and entered financed fees.
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
Port 180,000 at 3% and add 70,000 at 6%.
Combined payment = payment on ported balance + payment on additional balance and entered financed fees.
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
Porting is normally a new application and depends on lender approval, property, timing, and contract terms.
