FinToolSuite

Mortgage vs Personal Loan Calculator

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

Cheaper way to fund a large expense.

Compare cost of funding via mortgage top-up vs personal loan for the same amount. Enter amount needed and mortgage rate to see total interest of each.

What this tool does

Enter amount, mortgage rate/term, and personal loan rate/term. The tool shows total interest of each.


Enter Values

Formula Used
Monthly payment
Months
Principal

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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.

20,000 at 5% mortgage top-up over 15 years: 8,500 interest. Same 20,000 at 9% personal loan over 5 years: 4,900 interest. Personal loan wins total interest despite upper rate — shorter term dominates. Mortgage top-up has lower monthly payment but much higher total cost.

Quick example

With amount needed of 20,000 and mortgage rate of 5% (plus mortgage remaining term of 15 and personal loan rate of 9%), the result is 3,558.54. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.

Which inputs matter most

You enter Amount Needed, Mortgage Rate, Mortgage Remaining Term, Personal Loan Rate, and Personal Loan Term. Two inputs usually tip the answer one way or the other. Identify which ones matter most by flipping each value past a round threshold and watching whether the winning option changes.

What's happening under the hood

Standard amortisation for each path. Subtract to find interest difference. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.

What the headline rate hides

Lenders quote a rate; what you pay is a blend of that rate, fees, insurance, and any early-repayment penalty built into the product. The figure here isolates the core interest cost so you can compare like-for-like across deals — then add the other costs separately before signing anything.

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 vs personal loan produces a winner based on the inputs provided.

Inputs

Amount Needed:20,000 £
Mortgage Rate:5
Mortgage Remaining Term:15
Personal Loan Rate:9
Personal Loan Term:5
Expected Result£3,558.54

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 for each path. Subtract to find interest difference.

Frequently Asked Questions

Why does mortgage cost more total?
Long term. 15 years of interest even at 5% exceeds 5 years at 9%. Term dominates rate for total cost.
Why does mortgage have lower monthly?
Longer term spreads payment over more months. Cashflow-friendly but expensive overall.
Risk of mortgage top-up?
Converts unsecured debt to secured. Default risk shifts to home. Material risk increase.
Best use case for mortgage top-up?
Very large amounts (50k+), secured home equity available, low personal-loan rates unavailable. Weigh term carefully.

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