Mortgage calculator

Monthly payment from the property price, with tax and insurance. The formula and each step are shown below the result, so you can check the answer rather than take it on trust.

The formula

M = P · r(1+r)ⁿ / ((1+r)ⁿ − 1), where r is the monthly rate and n the number of payments. Subtract the deposit from the price to get the loan. Divide the annual rate by twelve. Raise (1 + monthly rate) to the number of payments. Then add monthly tax and insurance on top of the principal-and-interest figure.

What people get wrong

The headline payment is principal and interest only. Tax and insurance often add a third again on top, which is why a mortgage "affordability" figure taken from a payment calculator alone is routinely optimistic.

What this assumes

Rates and property taxes vary by lender and jurisdiction. This is illustrative, not an offer.

Questions

Why do you show the formula?

Because a number with no working is something you have to trust rather than something you can check. Showing the formula and the steps also answers the question sitting next to the calculation — people search for how to calculate a thing at least as often as they search for a tool that does it.

How do you handle rounding?

Money is rounded to two decimals on output, and schedules keep their running balances consistent so the final payment is trued up and the balance lands exactly on zero. Rounding is done deliberately at the end rather than accumulating quietly through the middle.

Are the tax and finance calculators up to date?

They compute correctly from the rate you give them. They do not know your jurisdiction, and any calculator whose answer depends on a rate or a filing rule says so on its own page. A calculator that silently assumes one country’s rate is wrong for everyone else and looks identical either way.