MORTGAGECALCULATOR
Multi-part mortgage calculator with full month-by-month balance breakdown. Model up to 3 parts on different rates and terms.
Property Details
LTV: 80.0% — Standard rates
Part 1
What does this mortgage calculator tell you?
This calculator works out your monthly repayment using the standard amortisation formula, then builds a full schedule showing your outstanding balance every month and year until the mortgage is cleared. It supports multi-part mortgages — where different portions are borrowed at different rates or over different terms — which is common for additional borrowing, Help to Buy equity loans, or part-and-part arrangements.
How to use this calculator
Enter your house valuation for the LTV calculation, then fill in Part 1 with your main mortgage amount, rate and term. If you have additional borrowing on a different rate or term, click Add Additional Borrowing Part.
House valuation
Enter the full property value. This is used only to calculate your LTV ratio — it doesn't affect the repayment calculation.
Part 1 — main mortgage
Enter the amount you're borrowing, the annual interest rate, and the term in years and months. Use the exact term offered by your lender for accuracy.
Additional parts
If you have further borrowing — a second charge, Help to Buy, or different rate tranche — click Add Part and enter those details separately.
Balance breakdown
After calculating, click View Monthly & Balance Breakdown to see a full amortisation schedule. Switch between yearly and monthly views, and between combined and individual parts.
The formula used
M is monthly payment, P is loan amount, r is monthly rate (annual ÷ 12), n is total months. Applied independently to each part, then summed for the combined total. The balance schedule runs month by month: interest = balance × r, principal = M − interest, new balance = previous balance − principal.
Tips & Best Practices
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Use years AND months for exact term matching — a 25-year 3-month mortgage is different from 25 years
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The LTV indicator tells you which rate tier you're in — 60%, 75%, 85% and 90% are key thresholds
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View the yearly breakdown to see how your balance drops — it falls slowly at first and accelerates later
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Additional borrowing parts are independent — each runs its own amortisation schedule
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Even overpaying £100/month on a £250,000 mortgage at 4.5% can save over £20,000 in interest
Frequently Asked Questions
M Singh CeMAP DipFA · 25+ Years UK Financial Services
Important Information
This calculator is for illustrative purposes only and does not constitute mortgage advice, a personal recommendation, or a mortgage offer.
Results are based on the figures you enter and assume a standard capital repayment structure. Actual rates, fees, terms, and eligibility will vary by lender and individual circumstances.
You should seek independent advice from a qualified mortgage adviser or broker before making any financial commitment.