Housing math, demystified.

Plug in real numbers, see the true cost of ownership, and the math behind every line.

Skip to reality check ↓30-yr fixed reference rate: 6.76% · Freddie Mac PMMS · 2026-09-15
$250,000
$

The total purchase price before taxes and fees. Type an exact amount or drag the slider.

6.76%
%

Edit freely — defaults to today's Freddie Mac average (6.76%). A 1% drop can save you hundreds monthly.

20% ($50,000)

20% or more avoids Private Mortgage Insurance (PMI). Your equity also cushions market dips.

Property tax varies wildly by state. Ohio's effective average is 1.56%.

30 years

A 15-year loan saves enormous interest but doubles your monthly payment. 30-year is the U.S. default.

Advanced Mode

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Fine-tune tax bracket, insurance, HOA, and existing debt payments.

22%

Your marginal federal income tax rate. Mortgage interest and property tax may reduce your taxable income if you itemize.

$120
$

Homeowner's insurance protects the structure. Required by every lender.

$0
$

Homeowner association dues. Common for condos and planned communities. $0 if not applicable.

$0
$

Minimum payments on car loans, student loans, credit cards, and personal loans. Lenders add these to your housing payment to compute back-end DTI.

Auto
$

Leave at $0 to auto-estimate PMI at 0.8%/yr of the loan when down payment is under 20%. Enter your lender's actual quote to override — PMI rates vary by credit score and loan program.

Investment Property Mode

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Model this property as a rental — cashflow, cap rate, after-tax return.

Reality check

"At 32% of a $65k household income, this home is stretching — manageable, but leaves little room for surprise."

Lenders will often approve you for more than you can comfortably afford. The 28/36 rule says no more than 28% of gross income to housing, and no more than 36% to all debt combined.

Want this scenario on paper?

Get your personalized Homebuyer Reality Check — 10-page PDF, your numbers, your state.

Compare loan terms

Same price · same rate
15-year fixed
$1,771/mo P&I
Lifetime interest: $118,767
Total paid: $318,767
20-year fixed
$1,522/mo P&I
Lifetime interest: $165,260
Total paid: $365,260
30-year fixed (current)
$1,299/mo P&I
Lifetime interest: $267,469
Total paid: $467,469

Shorter terms = bigger payment, dramatically less interest. The 30-year is the U.S. default because the monthly is lowest, not because it's cheapest.

Two tiny levers, big consequences. Both reflect everywhere below — schedule, payoff date, lifetime interest. Call your servicer first: some don't accept partial mid-month payments and may hold them in a suspense account.

Biweekly payments
Pay $649 every 2 weeks → 13 full payments/yr instead of 12.
$
Add this on top of every monthly check, marked "apply to principal".
Result vs. standard 30-year

Toggle biweekly or add an extra-principal amount to see how many months — and dollars — you can shave off.

Year-by-year amortization

Show schedule →

How each year of payments splits between interest (to the bank) and principal (your equity). In year one, almost everything is interest.

YearPrincipal paidInterest paidBalance remaining
1$2,127$13,455$197,873
2$2,276$13,307$195,597
3$2,434$13,148$193,162
4$2,604$12,978$190,558
5$2,786$12,796$187,772
6$2,980$12,602$184,792
7$3,188$12,394$181,604
8$3,410$12,172$178,194
9$3,648$11,934$174,546
10$3,902$11,680$170,643
11$4,175$11,408$166,469
12$4,466$11,117$162,003
13$4,777$10,805$157,226
14$5,110$10,472$152,116
15$5,467$10,116$146,649
16$5,848$9,735$140,801
17$6,256$9,327$134,546
18$6,692$8,890$127,854
19$7,158$8,424$120,696
20$7,658$7,925$113,038
21$8,192$7,391$104,846
22$8,763$6,819$96,083
23$9,374$6,208$86,709
24$10,028$5,555$76,682
25$10,727$4,855$65,955
26$11,475$4,107$54,480
27$12,275$3,307$42,204
28$13,131$2,451$29,073
29$14,047$1,535$15,026
30$15,026$556$0
Loan Amount
$200,000
Year-1 Interest
$13,455
Year-1 Property Tax
$3,900
Potential Tax Savings
$3,818
If itemized at 22%
Lesson 04 — Debt-to-Income

How lenders decide what you can afford.

Debt-to-Income (DTI) is the single most important number in underwriting. It's the percent of your gross monthly income that goes to debt. Lenders compute two versions:

  • Front-end DTI (the 28% rule)Housing payment ÷ gross income. Traditional ceiling: 28%.
  • Back-end DTI (the 36% rule)(Housing + all other debt) ÷ gross income. Traditional ceiling: 36%. Qualified Mortgage cap: 43%.

Adjust the affordability ratio and other debts above — the numbers on the right update in real time.

Your Numbers
Housing @ 28% front-end$1,744/mo
Other monthly debts$0/mo
Total debt (back-end)$1,744/mo
Gross income needed — front-end (28%)
$74,723/ year
Gross income needed — back-end (36%)
$58,118/ year
Whichever is higher = your real floor
$74,723/ year

That's $6,227 gross per month, or roughly $36/hour full-time.

Financial Literacy 101

Plain-language lessons
Understanding Escrow

Understanding Escrow

Why your lender holds your tax and insurance money — and how it shows up in your monthly payment as PITI.

The PMI Trap

The PMI Trap

Private Mortgage Insurance protects the bank, not you. Here's when it kicks in, how much it costs, and how to drop it.

Amortization Secrets

Amortization Secrets

In year one, ~80% of your payment is pure interest. One extra principal payment a year can shave 4–5 years off your loan.

ARM vs. 30-Year Fixed

ARM vs. 30-Year Fixed

Adjustable-rate mortgages start cheaper but reset to market rates after 5, 7, or 10 years. Here's when the gamble pays off.