Mortgage Term Reduction Calculator

200,000 at 5% over 25 years costs 350,000 total; over 20 years costs 317,000 — a 34,000 interest saving for an extra 150/month. The trade-off is higher monthly commitment. Most people pay down longer than they could afford to. Matching term to realistic monthly comfort rather than maximum comfort is worth modelling.

Quick example

With loan amount of 200,000 and annual rate of 5% (plus current term of 25 and shorter term of 20), the result is 33,975.27. 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 Loan Amount, Annual Rate, Current Term, and Shorter Term. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.

What's happening under the hood

Compute monthly payment at each term, total repayment, subtract to find interest saving. Standard amortisation. 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.

Worked example

Assume a loan of 300,000 at 4.5% annual rate:

• Over 30 years: monthly payment approximately 1,520; total repayment approximately 547,200; total interest approximately 247,200.
• Over 25 years: monthly payment approximately 1,690; total repayment approximately 507,000; total interest approximately 207,000.
• Interest saving: approximately 40,200.
• Monthly increase: approximately 170 per month.

The calculator models this trade-off by showing the interest difference. Whether the monthly increase is affordable depends on your income and other commitments.

Common scenarios

This calculator is useful in several situations:

• Inheritance or bonus arriving: exploring whether accelerating repayment makes financial sense.
• Rate drop at refinance: comparing whether to stick with the original term or shorten it at the new rate.
• Early career to stable income: moving from a longer-term loan to a shorter one as monthly headroom increases.
• Approaching retirement: modelling when the loan will clear relative to pension income.

What the result does and does not show

The calculator estimates the interest saved by moving to a shorter amortisation period at the same rate. It shows the maths of principal and interest alone. It does not account for opportunity cost (what that extra monthly payment might earn elsewhere), tax treatment of interest, changes to the rate during the loan term, lender penalties for early settlement, or your own cash flow priorities. It is a numerical illustration, not a financial forecast.

This calculator is for educational illustration only and does not constitute financial advice or a prediction of actual savings.