Finance · Mortgages & Home Finance

Mortgage Porting and Additional Borrowing Calculator

Combine the payment impact of a ported mortgage part and new borrowing while preserving their separate rates and terms.

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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

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.