Mortgage calculator: the listing price is a rumor — the payment is the fact. Form MC-10
House hunters do the math backwards: they fall for a listing price, then ask what it costs a month. The payment is the number that decides your next thirty years — principal and interest, plus the property tax the listing never mentions, the insurance, the HOA, and the PMI that shows up when the down payment comes up short. This page posts all of it as one monthly number, then lays the full year-by-year payoff ledger underneath.
Tool № 10 · Monday, September 28, 2026 · free, always
At 6.5%, every $100,000 borrowed costs $632.07 a month in principal and interest — before a dollar of tax, insurance, or PMI.
Input slip · Form MC-10
Two tabs, one ledger. Affordability solves your income backwards into a max purchase price; Monthly payment prices a specific house down to the dollar. Everything recalculates as you type, and everything stays in your browser — nothing is sent anywhere.
Prefilled at the Freddie Mac 30-year average for the week of Sept 24, 2026 — replace it with your actual quote.
Set to 6.5% for the worked example below (the Freddie Mac 30-year average for the week of Sept 24, 2026 was 7.03%) — replace it with your actual quote.
Posted entry · Form MC-10-R
More doors into the same ledger Form MC-10
Every angle on the mortgage, same arithmetic underneath:
How the ledger prices a house Form MC-10
The monthly payment is four or five lines, not one. Principal and interest come from the amortization formula lenders use themselves: on a $360,000 loan at 6.5% for 30 years it posts $2,275.44 a month, every month, for 360 months. That part never moves on a fixed-rate loan.
Then the escrow lines the listing never shows. Property tax — the 1.1% default here is $412.50 a month on a $450,000 price. Homeowner’s insurance — $1,800 a year is $150 a month. HOA dues, typed separately. And PMI: 0.5% a year on the loan when the down payment lands under 20%, which is $150 a month on a $400,000 example with 10% down, dropping off the month the balance crosses below 80% of the price.
Affordability runs the other direction. Lenders cap housing at 28% of gross monthly income, and at 36% of income minus your other debts — whichever is lower. This page solves that cap backwards into a purchase price, then checks whether the down payment you typed clears 20%. On $120,000 of income with $600 in monthly debts and $80,000 down, the 28% rule binds at $2,800 a month — which approves $401,821 at the prefilled 7.03% rate.
Common questions Form MC-10
What is PITI?
Principal, interest, property tax, and insurance — the four standard lines of a mortgage payment. This page adds PMI and HOA as further lines where they apply, and posts the whole stack as one monthly number.
When does PMI go away?
On a conventional loan PMI is required while the loan sits above 80% of the home’s value. This calculator charges 0.5% a year on the loan and drops it the month the balance crosses below 80% of the purchase price — on a $400,000 price with 10% down, that’s payment 95.
What is the 28/36 rule?
The two ratios lenders use: housing costs at or under 28% of gross monthly income (front-end), and housing plus all other debts at or under 36% (back-end). The lower of the two is your cap. On $120,000 of income with $600 in monthly debts, that’s $2,800 versus $3,000 — the 28% rule binds.
Is a bigger down payment always better?
It kills PMI at 20% and shrinks the loan, which shrinks every line downstream. But cash kept in reserve beats a slightly bigger down payment if the alternative is an empty emergency fund. The math here is neutral; the tradeoff is yours.
Does this handle adjustable-rate loans?
No — this calculator prices fixed-rate loans only: the rate you type is the rate for the whole term. Adjustable rates start lower and reset later, which is a different ledger.
Is this financial advice?
No. It’s amortization arithmetic on numbers you type: it doesn’t check your credit, approve loans, or know your local tax rate. A lender’s pre-approval and your own budget have the final word.