Work out your monthly payment and the total interest over the life of the loan — then see how much an extra payment each month saves you, in both interest and years. Nothing is sent to a server.
A mortgage is one of the biggest levers on when you reach financial independence. The complete FIRE Calculator folds your home — buying, the mortgage, running costs — into your whole life plan, alongside taxes, pensions and Monte Carlo stress-testing. Free and private.
Open the full FIRE planner →A repayment mortgage is an amortizing loan: you pay the same amount every month, but the split shifts over time. Early on, most of each payment is interest on a big balance; as the balance falls, more goes to principal. That's why the first years barely dent the balance — and why extra payments early are so powerful.
M = P · i · (1+i)n ÷ ( (1+i)n − 1 )
where P is the loan, i the monthly rate (annual ÷ 12) and n the number of monthly payments. The bar above shows how much of everything you repay is the original loan versus interest.
Every extra dollar you pay goes straight to principal — so it never accrues interest again for the remaining decades of the loan. A modest extra payment each month can shave years off the term and save a large multiple of itself in interest. Check it above by setting an extra amount.
Related: Compound interest · How long will my money last? · Coast FIRE.
Estimates only, not financial advice. Excludes property taxes, insurance, PMI and fees; assumes a fixed rate. Check exact figures with your lender. Your inputs stay in your browser — nothing is sent to a server. · Full planner · All calculators · Compound interest · How it works · Español · Português · Deutsch · Français · Italiano · Nederlands · Svenska · Norsk · Dansk · Polski · Čeština · Suomi · Ελληνικά · Türkçe · Bahasa Indonesia · Bahasa Melayu · 日本語 · 한국어 · 中文 · ไทย · עברית · العربية · Feedback