Methodology

Assumptions and formulas

This page explains exactly how calculations are produced so outputs stay transparent and deterministic.

Non-advice boundary

This tool provides illustrative calculations only. It is not financial advice, mortgage advice, or a recommendation.

Estimates are based on your inputs and assumptions. They exclude lender/product fees, taxes, penalties, eligibility criteria, and future uncertainty.

For personal recommendations, speak to a regulated mortgage adviser.

Repayment mortgage only (not interest-only).
No lender fees, taxes, legal costs, penalties, or insurance costs included.
Overpayment is a constant monthly amount.
Term reduction estimate assumes the same APR and continued overpayment for the full remaining term.
Rate sensitivity uses end-of-fixed balance and remaining term from base scenario.

Loan = property price - deposit.
Monthly rate = APR / 12.
Payment = P*r / (1 - (1+r)^-n), or P/n when APR is 0.
Fixed-period interest and end balance come from month-by-month amortization over 2/3/5 years.
Sensitivity scenarios use APR shifts of -0.25%, +0.25%, -1.0%, and +1.0% (floored at 0%).
LTV bands tracked in MVP: 95/90/85/80/75/60.