How this mortgage calculator works
People searching “how much house can I afford” usually want one number. The honest answer is that a calculator cannot give you that number, because affordability depends on your income, your debts, your savings, and the lender’s own rules. What a calculator can do is show you, line by line, how a home price turns into a monthly payment. Once you can see which inputs move the payment and by how much, the conversation with a lender gets much clearer.
The formula behind the payment
The principal-and-interest part of a fixed-rate mortgage uses the standard amortization formula:
Monthly P&I = L × r(1 + r)n ÷ ((1 + r)n− 1)
L is the loan amount (home price minus down payment, plus any fee rolled into the loan), r is the annual interest rate divided by 12, and n is the number of monthly payments (360 for a 30-year loan, 180 for a 15-year loan). Early in the loan most of each payment is interest; later, most of it goes to principal. The calculator then adds the monthly pieces a lender usually collects alongside the loan payment.
What each input means
- Home price. The purchase price you are modeling. You can also start from a monthly budget and let the calculator solve for a price that produces that payment.
- Down payment. The cash you put toward the price. A larger down payment lowers the loan amount and can change whether mortgage insurance applies.
- Interest rate and credit tier. The rate drives the principal-and-interest line. The CFPB’s Explore Interest Rates tool shows how credit score, down payment, term and loan type affect the rates lenders quote (as of September 2026).
- Loan term. A longer term spreads the balance over more payments, which lowers each payment but raises the total interest paid.
- Loan type.Conventional, FHA, VA and USDA loans have different down payment, insurance and fee rules. The calculator applies each program’s structure so you can compare them; your lender confirms what applies to you.
- Property tax, insurance and HOA dues. These are usually paid monthly through an escrow account set up by your lender, except HOA dues, which you normally pay to the association directly.
- Mortgage insurance. According to the CFPB, private mortgage insurance may be required on a conventional loan with less than 20 percent down, and it protects the lender, not you (as of September 2026).
- Discount points. Per the CFPB, points let you pay more up front in exchange for a lower rate, and one point equals one percent of the loan amount.
How lenders look at affordability
Lenders do not approve a loan from a payment alone. One measure they use is your debt-to-income ratio. The CFPB explains that you calculate it by adding up all your monthly debt payments and dividing by your gross monthly income. Limits differ by lender and loan program, so we do not suggest a target. The CFPB’s Buying a House guide covers the steps from preparing to shop through closing (as of September 2026).
When you apply, a lender must give you a Loan Estimate within three business days. That form, not a calculator, is where you see real terms and can compare lenders side by side.
A worked example, step by step
Say you enter a $400,000 home price. The calculator subtracts your down payment to get the loan amount, converts the annual rate to a monthly rate, and runs the formula above over 360 payments for a 30-year term. It then adds one-twelfth of the annual property tax and insurance you entered, any monthly HOA dues, and mortgage insurance if the loan type and down payment trigger it. Change one input at a time to see which line moves.
The calculator also shows how the real estate side of the purchase fits in. VroomBrick charges a 1% technology fee. Here is the only fee comparison we publish:
Worked example
On a $400,000 home, a 1% technology fee is $4,000. If a seller's agent charged 3%, that would be $12,000, a difference of $8,000. Commissions are negotiable, so your number depends on what you'd have paid.
What this calculator does not do
It does not check credit, quote a rate, or tell you what you qualify for. It is an educational estimate. VroomBrick is a technology platform, not a brokerage and not a lender, and nothing here is lending advice. For a focused view of every monthly homeownership cost, try the monthly cost breakdown. To see how a closing credit can work on the buyer side, try the buyer savings calculator.