Estimate your monthly mortgage payment, total interest, and full amortization schedule in seconds. This calculator also models extra payments, refinancing scenarios, and the true cost of taxes and insurance (PITI) so you can see what a home really costs to own — not just the loan payment.

Mortgage Calculator

Calculate monthly payments, total interest, and loan breakdown.

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Down Payment$70,000.00
Loan Amount$280,000.00
Total Interest$357,124.57
Total Paid$637,124.57
P&I Payment$1,769.79

Payment Breakdown

Annual Payment Split

Remaining Loan Balance Over Time

Cumulative Interest Paid vs. Principal Recovered

Early in the loan, most payments go to interest — see when the balance shifts

💡 Principal recovered exceeds cumulative interest at Year 0 — before this point, most of your payments fund interest.

Estimate your monthly mortgage payment, total interest, and full amortization schedule in seconds. This calculator also models extra payments, refinancing scenarios, and the true cost of taxes and insurance (PITI) so you can see what a home really costs to own — not just the loan payment.

Loan Term Comparison

15 vs 20 vs 30-year breakdown at 6.5% · $280,000 loan

15-Year Term

Monthly Payment$2,439.10
Total Interest$159,038
Total Paid$439,038
Interest Saved vs 30yr−$198,086

20-Year Term

Monthly Payment$2,087.60
Total Interest$221,025
Total Paid$501,025
Interest Saved vs 30yr−$136,099

30-Year Term

Monthly Payment$1,769.79
Total Interest$357,125
Total Paid$637,125

How This Calculator Works

A mortgage is an amortizing loan used to buy a home, repaid in fixed monthly installments across a set term (commonly 15 or 30 years). Each payment splits into two parts: principal, the borrowed amount you are paying back, and interest, the lender's fee calculated on the remaining balance. Because interest is charged on the outstanding balance, early payments are interest-heavy — a pattern called front-loaded amortization. Your down payment reduces the loan size; a 20% down payment also avoids Private Mortgage Insurance (PMI). Adding extra principal each month reduces the balance faster, which shrinks future interest and shortens the term. The PITI figure combines principal and interest with property tax and homeowners insurance to show your true monthly housing cost, which is what lenders use when qualifying you against a debt-to-income ratio.

The Mathematical Formula & Logic

The standard amortization formula for the fixed monthly principal-and-interest payment is M = P × [ r(1 + r)ⁿ ] / [ (1 + r)ⁿ − 1 ]. P is the loan principal (home price minus down payment). r is the monthly interest rate (annual rate ÷ 12, expressed as a decimal). n is the total number of monthly payments (loan term in years × 12). Total interest paid over the loan equals (M × n) − P. Each month the remaining balance updates as B_new = B_old × (1 + r) − M.

Worked Step-by-Step Example

Consider a $350,000 home with a 20% down payment on a 30-year fixed loan at 6.5% interest. The down payment is $70,000, so the loan principal P = $280,000. The monthly rate r = 0.065 ÷ 12 = 0.0054167, and n = 360 payments. Plugging into the formula gives a monthly P&I payment of about $1,771.66. Over 360 months you pay $637,798 total, of which $357,798 is interest. Adding a $200/month extra principal payment reduces total interest by roughly $97,000 and pays the loan off about 6 years early.

Frequently Asked Questions

P&I is just principal and interest. PITI adds property taxes and homeowners insurance to show your full monthly housing cost. Lenders qualify you on PITI when measuring debt-to-income, not on P&I alone.

Every extra dollar above your scheduled payment reduces principal directly. Because interest is charged on the remaining balance, a lower principal means less interest accrues each month — a compounding saving that also shortens the loan term.

PMI is required below a 20% down payment. By law it is automatically canceled at 78% loan-to-value, and you can request removal at 80% LTV with a good payment history. Extra principal payments help you reach that threshold sooner.

Refinancing pays off when the interest savings offset closing costs (typically 2–5% of the loan). A common rule is to refinance when rates drop at least 1% below your current rate and you will stay in the home past the break-even point shown in the Refinance tab.

Disclaimer: CompelKit tools and calculators are provided for educational and estimation purposes only and do not constitute certified legal, financial, or tax advice.

Read the full guide: How Mortgage Amortization Really Works →
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