Why this site exists
Most mortgage calculators online are lead-generation forms wearing a calculator costume. You enter your numbers, get a payment, and then a lender calls you for six weeks. Others hide the interesting part — the amortization schedule — behind an email address, or quietly omit property tax and insurance because the resulting number looks smaller and friendlier.
LoanMath does the opposite. Every calculator runs entirely in your browser, every assumption is visible and editable, and the full schedule is on the page rather than in a PDF. If the answer is uncomfortable, the site still shows it.
How the calculators work
All of the tools use the standard amortization formula for a fixed-rate loan:
M = P × r ÷ (1 − (1 + r)−n)
where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12) and n is the number of monthly payments. Interest is charged on the outstanding balance each month, and the remainder of the payment reduces principal. Extra payments are applied directly to principal after the scheduled payment, which is how servicers apply them when the payment is properly designated.
Property tax, homeowners insurance and HOA dues are treated as flat monthly amounts inside escrow. PMI is modelled month by month and stops automatically when the balance reaches 80% of the original purchase price. The schedule zeroes out exactly on the final payment, with the last installment adjusted for accumulated rounding — the same behavior you see on a real statement.
What the models exclude
- Closing costs, prepaid interest, lender fees and recording taxes
- Escrow shortages, supplemental tax bills and insurance premium changes
- Adjustable-rate resets, interest-only periods and balloon payments
- Prepayment penalties, late fees and forbearance
- Tax deductibility of mortgage interest, which varies by jurisdiction and filing status
Every result is an estimate built from the inputs you provide. A lender's Loan Estimate is the document that matters.
Editorial standards
Rates, tax rates and cost ranges quoted in the explanatory text are representative US figures for 2026 and are updated when they drift materially. The calculators do not use live rate feeds — you enter the rate you were quoted, which is more accurate than any national average. We do not accept payment for placement in calculator results, and no lender can pay to appear on this site.
Privacy by default
There is no login, no database of loan scenarios, and no analytics script watching which numbers you type. Your inputs stay in the browser tab. The one thing stored locally is your currency preference, so the site does not reset to dollars every visit. Advertising, when present, is served by Google AdSense under its own cookie rules — see the privacy policy for the details.
Corrections
If a formula, a default or an explanation is wrong, we want to know. Email the address on the contact page with the page and the number you expected. Corrections that affect a calculation are fixed and noted.
LoanMath is not a lender, mortgage broker, real estate agent or financial adviser, and nothing on this site is a commitment to lend or a personalized recommendation.