FinToolSuite

Mortgage Debt Consolidation Calculator

Updated April 17, 2026 · Mortgage · Educational use only ·

Interest saved by rolling debt into a mortgage.

Compare total interest on high-rate debt kept separate versus consolidated into your mortgage. Enter debt to consolidate and debt rate for an instant result.

What this tool does

Enter the debt to consolidate, its current rate, and your mortgage rate. The tool shows the interest saved over the debt's remaining term.


Enter Values

Formula Used
Debt principal
Amortised monthly payment
Number of monthly payments

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Disclaimer

Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.

Consolidating high-rate debt into a mortgage lowers the rate but stretches repayment. At 22% credit card rates vs a 5% mortgage, the rate gap looks overwhelming — but the trap is term length. 15,000 of credit card debt at 22% paid over 5 years costs about 9,800 in interest. Rolling into a 25-year mortgage at 5% costs about 11,300 in interest — a touch worse, despite the lower rate, because the debt sticks around five times longer. Keep the term short and consolidation can help; stretch it to the full mortgage and you lose.

How to use it

Enter debt amount, its current rate, the remaining years on it, and your mortgage rate. The tool shows total interest in each scenario and the saving or loss.

Run it with sensible defaults

Using debt to consolidate of 15,000, current debt rate of 22%, current payoff term of 5, mortgage rate of 5%, the calculation works out to 1,449.53. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.

The levers in this calculation

The inputs — Debt to Consolidate, Current Debt Rate, Current Payoff Term, Mortgage Rate, and Mortgage Term — do not pull with equal force. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.

How the math works

Standard amortisation applied to each scenario. Interest paid = total payments minus principal. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".

Why this matters before you sign

A mortgage is usually the biggest single financial commitment a person makes. The difference between a well-chosen product and a hasty one can run into tens of thousands over the life of the loan. Running the numbers here before committing is the cheapest form of due diligence available.

What this doesn't capture

The figure excludes arrangement fees, valuation costs, legal fees, insurance, and any early-repayment charges — those can add several thousand to the headline cost. Rate changes at renewal for fixed-term deals will shift the picture further. Use this for the core interest/principal math and add the other costs on top.

Example Scenario

Mortgage debt consolidation produces a saving figure based on the inputs provided.

Inputs

Debt to Consolidate:15,000 £
Current Debt Rate:22
Current Payoff Term:5 years
Mortgage Rate:5
Mortgage Term:25 years
Expected Result£1,449.53

This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.

Sources & Methodology

Methodology

Standard amortisation applied to each scenario. Interest paid = total payments minus principal.

Frequently Asked Questions

Why can consolidation lose money?
Stretching short-term debt over a 25-year mortgage can pile up more total interest even at a much lower rate. Term length matters as much as rate.
Can I consolidate without extending?
Yes — if you keep the same payoff horizon, lowering the rate always saves. The saving only reverses when you stretch the term.
Are there other costs?
Remortgage fees, valuations, and potentially early-repayment charges on the existing mortgage. Add these to decide the real break-even.
What about secured vs unsecured?
Rolling unsecured debt into a mortgage secures it against the property. Missed payments can now threaten the home — a meaningful risk change beyond pure interest.

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