LuniMortgage · A Lunibyte financial tool
Real rates from public Federal Reserve data — and the full monthly payment, not the teaser. Plus a promise the big bank sites won't make: we never sell your information to lenders. No lender will ever call you from this page.
How these numbers are made — and why your lender's quote will differ — is explained in Methodology below.
| Year | Interest | Principal | Balance |
|---|
Estimates only — see the methodology and disclaimer below. Your inputs are stored only in this browser (local storage) so the page remembers them; they are never transmitted anywhere. There is no account and nothing to sell — that's the point.
Your monthly principal & interest is the standard amortization formula: the loan is repaid in equal monthly payments over the term, each payment first covering that month's interest on the remaining balance. On top of that we add the costs lenders roll into escrow — property tax, homeowner's insurance, HOA dues, and PMI when it applies — because a payment you can't see whole is a teaser, not a number. Extra monthly payments go entirely to principal, which is why they shorten the loan so powerfully.
The weekly anchors are Freddie Mac's Primary Mortgage Market Survey — the industry's benchmark averages — fetched from FRED, the Federal Reserve Bank of St. Louis database. Because that survey prints weekly, we adjust it daily by the move in Treasury yields (10-year for the 30-year rate, 5-year for the 15-year) to estimate today's level. Your credit tier then adjusts the market rate by a typical amount (−0.25% at 780+ up to +1.25% below 660). Averages assume a strong borrower with 20% down; your real quote will differ by lender, points, loan type and timing — anyone who promises you one exact rate for everyone is selling something.
Every calculation happens in this page, on your device. The only network call this page makes is fetching the public rate data above — your numbers are never sent anywhere, and Lunibyte has no lender partners and sells no leads. Clear your browser data or hit Reset and everything is gone.
From Freddie Mac's Primary Mortgage Market Survey (weekly national averages) via FRED, the Federal Reserve Bank of St. Louis database, adjusted daily by the movement in US Treasury yields. The anchor date and the Treasury date are printed right under the numbers, and the figures refresh automatically — no lender pays to be listed, because no lender is listed.
A mortgage rate is personal: it depends on your credit score, down payment (loan-to-value), whether you pay points, the loan type and size, your state, and the day you lock. Published averages describe a strong, typical borrower. Pick your credit tier above to see a more realistic estimate for you — then expect individual lenders to land within a few tenths of it, in either direction.
Private mortgage insurance protects the lender — not you — when the down payment is under 20% on a conventional loan. We estimate it at 0.55% of the loan per year. By law it must be removed automatically when your balance reaches 78% of the home's original value, and you can request removal at 80%.
This calculator prices a payment; affordability is the bigger picture. A common guardrail keeps housing costs near or below 28% of gross income, but your real answer depends on your other debts and savings goals. For the long view — when work could become optional — try LuniBound, our retirement planner.
No. LuniMortgage is an educational calculator. Its rates are national averages and estimates, not a quote, pre-approval, or offer of credit; Lunibyte is not a lender or mortgage broker. Talk to licensed professionals before signing a loan.
When could work become optional? Your FI number, freedom age and a plan stress-tested against real market history — the long game beyond the mortgage.
Already have a loan? Compare it against today's rates with a true break-even — fees, interest and the restarted clock all counted.
Still deciding whether to buy at all? Net-worth math for the oldest argument in housing, with today's rates.