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Mortgage Calculator

Estimate your monthly payment, total interest and amortization in seconds.

Extra payments (optional) +

Result —

About this calculator

A mortgage calculator lets you model the cost of a home loan before you sign anything. By trying different combinations of loan amount, interest rate and term you can quickly understand how much house you can comfortably afford and how a higher rate or longer term changes the total interest you pay over the life of the loan.

How it works

The calculator uses the standard amortizing-loan formula. Each month a fixed payment covers part of the interest accrued since the previous payment and part of the principal still owed. Early in the loan most of the payment goes to interest; over time the balance shifts and more of each payment reduces the principal.

Changing the interest rate has a large effect on the total cost. For a 30-year mortgage, a one-percentage-point increase typically adds tens of thousands of currency units in interest paid over the life of the loan, even though the monthly difference looks small.

Shortening the term — for example, switching from a 30-year to a 15-year mortgage — increases the monthly payment but dramatically reduces total interest because the principal is repaid much faster.

Many lenders also charge property tax, homeowners insurance and (where applicable) private mortgage insurance on top of the principal and interest. This calculator focuses on principal-and-interest only — the core mortgage cost — so the numbers stay directly comparable across lenders.

Formula

M = P · ( i · (1 + i)^n ) / ( (1 + i)^n − 1 )

M = monthly payment
P = principal (loan amount)
i = monthly interest rate (annual rate / 12)
n = total number of payments (years × 12)

Examples

30-year fixed at 6%

A 300,000 loan at 6% over 30 years costs roughly 1,798 per month. Over the full term you repay more than twice the amount you borrowed because of compounding interest.

Result: Monthly payment ≈ 1,798.65 — total interest ≈ 347,514

15-year fixed at 6%

Switching the same loan to 15 years raises the monthly payment by about 733 but cuts total interest by more than half.

Result: Monthly payment ≈ 2,531.57 — total interest ≈ 155,683

Frequently asked questions

What is the difference between APR and interest rate? +
The interest rate is the cost of borrowing the principal. APR (annual percentage rate) bakes in most of the loan’s fees and points so it’s a better number for comparing offers across lenders.
Should I choose a 15-year or 30-year mortgage? +
A 15-year mortgage has a lower interest rate and dramatically less total interest, but a higher monthly payment. Choose the longest term whose monthly payment fits your budget comfortably, then prepay if you can.
Does this calculator include taxes and insurance? +
No — it shows principal and interest only. Property tax, homeowners insurance and PMI vary by region and lender; add them separately when you compare full housing cost.
How much can I save by making extra payments? +
Even small extra payments toward principal can shave years off a mortgage and save tens of thousands in interest. Use the schedule to see how a one-time or recurring extra payment changes the timeline.
Is the result accurate? +
The math is exact for a fixed-rate, fully amortizing loan. Your real lender quote may differ slightly because of rounding, day-count conventions or escrow setup.

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