About

Homeowner Calculator is a set of free US mortgage calculators for buying, paying down, refinancing and borrowing against a home.

Who builds it

These tools are built by an independent site owner, not a licensed mortgage professional. The formulas are described below. The payment, amortization, refinance and HELOC maths has been checked against published government examples and two independent implementations. The affordability and rent-vs-buy tools are simplified models with assumptions you can edit. Found a mistake? Tell us.

What it does and does not do

• It calculates estimates from the numbers you enter, in your browser.
• It does not show current rates, quote rates or compare lenders, and we do not rate or recommend lenders or products.
• It does not ask for your contact details to see a result, and we do not send the numbers you enter to our servers. See the Privacy Policy.

Method

• Monthly payment. The standard fixed-rate formula: loan × r / (1 − (1 + r)⁻ⁿ), where r is the annual rate divided by 12 and n is the number of payments. It is worked out in exact arithmetic and rounded up to the next cent.
• Amortization and extra payments. Each month the interest is the balance times r, rounded to the nearest cent. The rest of the payment, plus any extra, reduces the balance. Interest saved compares the schedule with extra payments against the same loan without them.
• Refinance. Monthly saving is the current payment minus the new payment. Break-even is shown two ways: closing costs divided by the monthly saving (only when you pay the costs in cash), and the first month in which the interest saved covers the costs. Enter principal and interest only for your current payment.
• Cash-out refinance, HELOC and home equity loan. The new loan is the balance plus the cash (plus costs if added). Loan-to-value and combined loan-to-value are compared with a limit you set. A HELOC interest-only payment is the balance times the rate divided by 12; repayment is a level payment over the repayment period.
• Closing costs. The total of the fees you enter, with percent fees rounded up to the cent, plus prepaid interest (one day of interest times the days) and escrow deposits. No fee amounts or tax rates are built in.
• Affordability. A simplified rule of thumb: the lower of 28% of gross monthly income, and 36% minus your monthly debts. The price is the highest whose full monthly payment fits that budget. Taxes, insurance, PMI and HOA dues count only if you enter them. Lenders set their own limits; this is not a pre-approval.
• Rent vs buy. A simplified month-by-month comparison of the buyer’s net wealth and the renter’s invested savings, using assumptions you enter and can edit. It leaves out taxes and many real-life factors, and the break-even can move by years when one assumption changes by a point.

Rounding

Payments, fees and other costs are rounded up to the next cent, and amounts you could receive or borrow are rounded down. This is a choice we made, not a lender rule. Because many lenders round to the nearest cent, a result can differ from lender documents by a cent. Worked examples that reproduce a published figure are shown rounded to the nearest cent so they match the source. The calculators leave out taxes, escrow, PMI and fees unless you enter them.

Sources

Sources consulted, listed by name:

• Consumer Financial Protection Bureau (CFPB), sample Loan Estimate (Regulation Z model form H-24B)
• CFPB, Loan Estimate and Closing Disclosure forms (12 CFR 1026.37 and 1026.38)
• CFPB, What you should know about home equity lines of credit
• Federal Reserve Board, A Consumer’s Guide to Mortgage Refinancings
• Regulation Z, Truth in Lending, Appendix J (12 CFR Part 1026)
• Fannie Mae Selling Guide, B3-6-02 Debt-to-Income Ratios and B3-6-03 Monthly Housing Expense for the Subject Property

Last reviewed: October 2026.

See also the Terms of Use and the Privacy Policy.