UK planning estimate

United Kingdom Mortgage Planning Calculator

Estimate a fixed-rate repayment mortgage and add the actual annual Council Tax, annual home insurance, and upfront purchase tax you enter. This is not an affordability assessment or tax determination.

Home price (£)

Down payment (£)

Repayment period (Years)

User-entered annual nominal interest rate (%)

Actual annual Council Tax (£)

Actual annual home insurance (£)

Actual upfront SDLT, LBTT, LTT or other purchase tax (GBP) Use the official calculator for the property jurisdiction and your buyer circumstances; enter 0 if none.

Estimate

Estimated total monthly amount

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Monthly principal and interest — Monthly Council Tax — Monthly home insurance — Upfront purchase tax entered — Total interest over the selected term — Nominal total over selected term —

Monthly amount breakdown

Annual principal and interest schedule

Balance over time

The nominal total repeats today’s entered Council Tax and insurance for the whole term without inflation.

Sources: GOV.UK SDLT scope and official residential rates and calculator.

GUIDE

Mortgage planning guide

What the estimate includes

Monthly principal and interest use a fixed-rate annuity formula. Annual Council Tax and home insurance are divided by 12. The upfront purchase-tax amount you enter is shown separately and included once in the nominal total.

Why purchase tax is user entered

SDLT applies in England and Northern Ireland, while Scotland and Wales use different transaction taxes. Buyer status, additional-property rules, residence, reliefs and transaction structure change the amount. Use the relevant official calculator and enter the result.

Planning boundary

The calculator does not assess affordability, eligibility, product fees, rate resets, early repayment charges or future Council Tax and insurance changes. The nominal total is not a lender disclosure.

Extra payment and refinance comparison

Compare a remaining loan, recurring extra payments, and a hypothetical refinance using rates and costs you enter.

GBP

Current balance Current annual rate (%) Remaining term (months) Extra payment each month Refinance annual rate (%) Refinance term (months) All refinance costs and penalties Planned time before sale/refinance (months) Plan start month

Scenario comparison

Scenario	Scheduled monthly payment	Payoff	Total interest	Upfront cost/cash	Difference vs baseline interest

Refinance cash-flow break-even—

Cash-flow change during planned hold—

Extra-payment time saved—

Monthly schedule

Scenario shown

The on-screen table shows the first 24 months and final month. CSV export includes every simulated month.

Month	Payment	Principal	Interest	Balance

Assumptions, worked example, and source

Rates are user-entered; no current lender rate or product recommendation is supplied. Most countries use annual rate ÷ 12. Canada uses nominal semi-annual compounding converted to a monthly rate.
Extra payment is applied after scheduled interest with no prepayment charge. Enter any early-repayment charge in refinance costs and confirm overpayment limits with the lender.
Refinance break-even accumulates monthly payment differences until they recover upfront costs. It is a cash-flow measure, not an equity, tax, opportunity-cost, or approval analysis.
The default worked example compares one remaining balance over its remaining term. Replace every assumption with the current statement and a formal refinance quote.

Consumer authority mortgage reference for this country · Method reviewed 2026-07-30.