Mortgage Calculator

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Monthly Payment
Total Interest Paid
Total Cost
Payoff Timeline

Note: Results show principal and interest only. This calculator does not constitute financial advice. Consult a licensed mortgage professional for personalised guidance. Not financial advice.

Formula

M = P × r(1+r)^n / ((1+r)^n − 1) | r = annual_rate ÷ 12, n = years × 12

Worked Example

Inputs

Loan Amount (P)
$300,000.00
Annual Interest Rate
6%
Loan Term (n)
30 years (360 monthly payments)
Monthly Rate (r)
0.50% per month

Result

Monthly Payment (M)
$1,798.65
Total Interest Paid
$347,515.44
Total Cost (Principal + Interest)
$647,515.44
Loan Term
360 months
A $300,000.00 loan at 6% annual interest over 30 years has a monthly payment of $1,798.65. Over the life of the loan you will pay $347,515.44 in interest, bringing the total cost to $647,515.44. This calculator provides an estimate of principal-and-interest payments for a fixed-rate mortgage based on the information entered. Results are for informational purposes only and are not a loan estimate, loan offer, approval, or financial advice. Actual mortgage costs may differ and may include property taxes, homeowners insurance, mortgage insurance, HOA fees, points, closing costs, escrow items, lender fees, and other costs not included here. Consult a qualified mortgage lender, financial advisor, or housing counselor before making borrowing decisions.

Frequently Asked Questions

What is the formula for calculating a mortgage payment?
The standard fixed-rate mortgage formula is M = P × r(1+r)^n / ((1+r)^n − 1), where M is the monthly payment, P is the loan amount (principal), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). For a $300,000 loan at 6% for 30 years: r = 0.005, n = 360, M ≈ $1,798.65.
How much of each mortgage payment goes to interest vs principal?
In the early years, most of each payment covers interest. On a $300,000 loan at 6% for 30 years, the first payment of $1,798.65 is split roughly $1,500 interest and $299 principal. By year 20, the split reverses. This pattern is called amortization — the year-by-year schedule shows the exact breakdown for your loan.
What happens if I make extra mortgage payments?
Extra payments go directly to reducing the principal, which reduces future interest charges and shortens the loan term. Adding $500 per month to a $300,000 30-year loan at 6% cuts the payoff time from 30 years to roughly 21 years and saves over $100,000 in interest. The calculator's extra monthly payment field shows the exact impact.
What is the difference between interest rate and APR on a mortgage?
The interest rate determines your monthly payment using the standard amortization formula. APR (Annual Percentage Rate) includes the interest rate plus fees such as origination charges, points, and mortgage insurance, expressed as an annualized rate. APR is always equal to or higher than the interest rate. Use APR to compare loan offers; use the interest rate for monthly payment calculations.
Does this calculator include property taxes, insurance, and PMI?
No — this calculator computes the principal and interest (P&I) portion of your mortgage payment only. Your actual monthly housing cost will also include property taxes, homeowner's insurance, and if your down payment is less than 20%, private mortgage insurance (PMI). Add these costs separately to get your total monthly obligation.
How is total interest calculated over the life of a mortgage?
Total interest = (monthly payment × number of payments) − loan amount. For a $300,000 loan at 6% for 30 years: total paid = $1,798.65 × 360 = $647,514; total interest = $647,514 − $300,000 = $347,514. The amortization schedule shows interest paid each year, which front-loads the highest interest costs.

Source & Methodology

Tier 1 — Government / Official
CFPB: How do mortgage lenders calculate monthly payments?
CFPB states that most mortgage principal-and-interest payments are calculated using a standard mathematical formula based on loan amount, loan term, and interest rate.
Tier 1 — Government / Official
CFPB: How does paying down a mortgage work?
CFPB describes mortgage amortization and states that lenders use a standard formula to calculate payments that pay off the loan at the end of the term.
Tier 1 — Government / Official
Federal Reserve FEDS: The Interest Rate Elasticity of Mortgage Demand
Federal Reserve source gives the fixed-rate mortgage monthly payment formula equivalent to M = P × r(1+r)^n / ((1+r)^n − 1).

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