Overpayment, amortization, rent vs buy, loan comparison. Enter your numbers and get your answer in seconds. No signup. No account. Nothing stored.
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See how much extra monthly payments — or a one-off lump sum — save you in total interest and shorten your mortgage term. Works for fixed-rate mortgages in the US, UK, and Canada. Adjust the inputs and watch the numbers change in real time.
Try the overpayment calculatorFull schedule
Generate a full payment-by-payment schedule showing exactly how much of each payment goes to interest versus principal. Expand any year for a month-by-month breakdown — useful for sanity-checking lender statements or planning a payoff strategy.
Build my amortization scheduleLifestyle math
Is it actually cheaper to buy than rent where you live? This calculator compares total housing costs over time — including property tax, maintenance, home appreciation, and what your down payment could earn if invested instead. Real numbers, not generalisations.
Run the rent vs buy comparisonSide by side
Comparing two mortgage offers? Enter the rate, term, and closing costs for each and see the true cost difference over the life of both loans. Useful when deciding between a 15-year and 30-year fix, or weighing whether to pay points upfront.
Compare my loan optionsMost mortgage calculators are built by banks or comparison sites with something to sell. Mortgage Toolkit is different. All four calculators run entirely in your browser — your numbers never leave your device, no account is required, and no personal information is collected.
All calculations happen locally in your browser. Nothing is sent to a server. Nothing is stored between sessions.
Switch between dollars, pounds, and Canadian dollars in one click. The calculators are built to reflect how mortgages work in each market.
No submit button, no loading screen. Change any input and the result updates immediately — so you can explore different scenarios in real time.
Short reads you can finish in a few minutes — written to pair with the calculators above.
Browse all guides →Pick the calculator that matches your question. Adjust the inputs until the result surprises you. That number is the one worth knowing.