Mortgage Calculator

📖 Tool Introduction

A mortgage is the largest outlay most people ever take on, yet the contract usually shows only the monthly payment and the term, not what the borrowing actually costs.

This calculator lays out both repayment methods in full. Equal instalment keeps the payment level and front-loads interest, so early payments are mostly interest and little principal. Equal principal fixes the principal each month while interest falls with the balance, so the first payment is the largest and they shrink from there.

Enter the amount, term and rate to see the first payment, total repaid, total interest and a complete period-by-period schedule. The prepayment field models a lump sum in a chosen month and shows how much interest it saves.

Every figure you type stays inside this browser tab. The arithmetic runs as plain JavaScript on your own device, so nothing is uploaded to a server, nothing survives after you close the page, and there is no account to create or sign in to. You can enter real numbers without worrying about them leaving your machine.

What comes out is a mathematical projection built on the assumptions you supply, and the assumptions are the part worth checking. Real outcomes turn on details no calculator can see: the exact wording of a loan contract, the policy in force in your city this year, the way your own body responds. Use these numbers to orient yourself and to compare one option against another, then confirm anything that carries real consequences against an official document or a professional who can look at your actual circumstances rather than a generic formula. Where a result feeds into a decision that costs money or affects your health, treat it as the opening of a conversation with someone who can see the whole picture rather than as the answer in itself.

The inputs here are deliberately plain: no file to upload, no network call, no queue to wait in. That keeps the tool fast and private, and it also means no record exists anywhere of what you calculated, so nothing you try here can come back to you later.

✨ Key Features

• Switch between equal instalment and equal principal to compare
• First payment, total repaid, total interest and total principal
• Full schedule: period, payment, principal, interest, balance
• Prepayment modelling at a chosen amount and month
• Any combination of rate, amount and term recalculates instantly
• Recalculates the moment you change any figure, with no waiting and no separate submit step

🚀 How to Use

1. Enter the loan amount in ten-thousands, the term in years and the annual rate
2. Choose the repayment method on the right
3. To model a prepayment enter the amount and month number, or zero to skip
4. The result panel shows the headline figures and the schedule below
5. Reset clears every field back to its default

⚠️ Things to Note

• Calculation basis: Results follow the standard formulas and ignore rate resets, LPR repricing and interest on the days between drawdown and the first payment. Your bank schedule is authoritative
• Prepayment method: Prepayment is modelled as reducing the balance while keeping the term, which differs from the shorten-the-term option some banks offer; that option saves more interest
• Combination loans: Provident fund loans and combination loans need each tranche calculated separately at its own rate, then added together
• Computed locally in your browser: Every figure is worked out inside your own browser and nothing is sent to a server. The values disappear when you close the page, so you can safely enter real numbers
• Indicative results only: What you see here is a mathematical projection. For contracts, tax filings or medical decisions, rely on the official documents issued by the relevant authority rather than on this tool