Mortgage Calculator — Monthly Payment & Interest
Enter your home price, down payment, loan term, and interest rate to instantly see your monthly payment, total interest paid, and full cost breakdown. No signup, runs entirely in your browser.
How the Mortgage Calculator Works
- 1Enter the home price — the full purchase price of the property.
- 2Set the down payment as a dollar amount or percentage. A note appears if the down payment is below 20% (PMI is typically required in that case).
- 3Choose a loan term — 15, 20, 25, or 30 years. Switching terms updates all results instantly so you can compare.
- 4Enter the annual interest rate. Results — monthly payment, total interest, total cost, and the principal vs interest split — update immediately.
Understanding the Amortization Split
The coloured bar shows how your total payments divide between principal (repaying the loan) and interest (the lender's cost). On a 30-year mortgage at typical rates, more than half of what you pay goes to interest rather than building equity. Shortening the term or increasing the down payment shifts that balance significantly — a 15-year mortgage at the same rate can cut total interest paid by 40% or more even though the monthly payment is higher.
Tips for Getting the Best Mortgage
Put 20% down if possible
Crossing the 20% down payment threshold eliminates PMI, which saves 0.5–1.5% of the loan annually. On a $400,000 loan, that is $2,000–$6,000 per year until you reach 20% equity naturally.
Compare 15 vs 30-year terms
The 30-year monthly payment is lower, but the total interest can be double the 15-year cost. Use the term buttons to see the exact difference for your loan — then decide if the lower payment is worth the long-term cost.
Test rate sensitivity
Even a 0.5% rate difference has a significant long-term impact. Try your rate at +0.5% and −0.5% to understand your exposure to rate changes before locking in.
Factor in the full monthly cost
Add property tax (typically 0.5–2% of home value per year), homeowner's insurance (~$1,000–$2,500/yr), and PMI if applicable to the payment shown here to get your real monthly outlay.
Budget total cost, not just monthly
The total cost figure shows what you actually pay including interest. On a $400,000 loan at 6.5% over 30 years, total interest alone exceeds $500,000 — knowing this helps you prioritise paying down principal early.
Use for refinancing comparisons
Enter your remaining balance as home price and $0 down payment, then compare your current rate vs a refinance rate to see the monthly savings and whether the break-even makes sense given closing costs.
Frequently Asked Questions
How is the monthly mortgage payment calculated?
The standard formula is M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the total number of monthly payments (years × 12). This assumes a fixed-rate loan with equal monthly payments throughout the term.
What is included in the monthly payment shown?
The payment shown is principal + interest only. It does not include property taxes, homeowner's insurance, or private mortgage insurance (PMI). In practice, these are often included in an escrow payment collected by the lender, so your actual monthly outlay will be higher.
What is PMI and when is it required?
Private Mortgage Insurance (PMI) is typically required when your down payment is less than 20% of the home price. It protects the lender if you default. PMI usually costs 0.5–1.5% of the loan amount per year and can be cancelled once you reach 20% equity. The calculator flags this when your down payment falls below 20%.
What is the difference between a 15-year and 30-year mortgage?
A 30-year mortgage has a lower monthly payment but you pay significantly more total interest over the life of the loan. A 15-year mortgage has a higher monthly payment but builds equity faster and costs much less in total interest — often 40–50% less. Use the loan term buttons to compare both scenarios instantly.
Does a higher down payment lower my monthly payment?
Yes. A larger down payment reduces the loan principal, which directly lowers the monthly payment and the total interest paid. It also helps you avoid PMI if you reach 20% down, and may qualify you for a better interest rate.
Does this calculator store or transmit any of my data?
No. All calculations run entirely in your browser using JavaScript. Nothing is sent to any server. Your home price, income, or financial details are never logged or stored.
What interest rate should I use?
Use the current average rate for your loan type as a starting estimate — you can find these on financial news sites or from your lender. Rates vary based on credit score, down payment, loan type, and market conditions. Try several rates to see how sensitive your payment is to rate changes.
Can I use this for refinancing calculations?
Yes. Enter your remaining loan balance as the home price and set the down payment to $0. Enter the new term and rate you are considering. The resulting monthly payment and total interest reflect the refinanced loan. Compare against your current remaining balance to evaluate whether refinancing makes sense.