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Mr B says: The total interest over a 30-year mortgage is often more than the original loan amount. Even small extra repayments each month can shave years off the term.How amortisation actually works
A fixed monthly loan payment stays the same throughout the term, but the split between interest and principal inside that payment changes every month. Early payments are weighted heavily toward interest because the outstanding balance is still large. As the balance shrinks, more of each payment goes toward principal, and the interest portion shrinks with it. This is why paying off a mortgage feels slow for the first several years and then accelerates noticeably in the back half of the term.
Term length is a trade-off, not just a monthly number
A shorter loan term means a higher monthly payment but dramatically less total interest paid, because the balance is reduced faster and there's less time for interest to accrue on it. A longer term lowers the monthly payment but can roughly double the total interest paid over a 30-year mortgage compared to a 15-year one at the same rate. Run both terms through this calculator before deciding — the difference is usually much larger than people expect.
Where extra repayments make the biggest difference
Because early payments are interest-heavy, extra repayments made early in the loan have a bigger compounding effect than the same extra repayment made later on. If overpaying is an option, doing it as early as possible in the loan term gets more value per dollar than waiting.
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