The 28% Rule Is Wrong in Washington. Here's What to Use Instead.
The standard advice is to keep housing under 28% of gross income. In Washington that rule is miscalibrated in both directions at once — and understanding why gives you a genuine advantage over buyers applying it mechanically.
Where the rule comes from
The 28% front-end ratio is a lender's underwriting convention, not a household budgeting principle. It exists because it predicted default reasonably well across a national portfolio. It was never calibrated to your state, your tax burden, or your commute.
Two things make it wrong here, and they push in opposite directions.
Reason one: no state income tax
Washington is one of nine states with no personal income tax. A gross-income rule silently assumes a typical state tax burden that you simply do not pay.
On $150,000, single filer, standard deduction, no retirement contributions:
| Annual | Monthly | |
|---|---|---|
| Gross income | $150,000 | $12,500 |
| Federal income tax | −$24,698 | −$2,058 |
| FICA | −$11,475 | −$956 |
| State income tax | $0 | $0 |
| Take-home | $113,827 | $9,486 |
The same $150,000 in Oregon or California leaves noticeably less. So a Washington buyer applying a national 28% rule is being more conservative than the rule intends — they have more spendable income behind each dollar of gross than the rule assumes.
That's why this site uses 33% of gross as its default rather than 28%. At $150,000 that's $4,125 a month instead of $3,500 — and it still lands at 43% of actual take-home, which is a defensible place to be.
Reason two: property tax is low, but prices are not
Washington's effective property tax rates are moderate — King County County runs 0.84%, and rural counties go as low as 0.57%. Compare New Jersey or Illinois at well over 2%.
But a percentage of a large number is still a large number. 0.84% of $853,410 is $7,169 a year, or $597 a month, before you've paid a cent of principal.
So the low-rate advantage is real but smaller than it sounds, and a rule of thumb built on principal and interest alone will understate your true cost. Always reason in full PITI — principal, interest, taxes, insurance — not the payment a listing site quotes you.
What to use instead
Measure against take-home, not gross. Gross is a lender's unit because it's verifiable. Your mortgage comes out of net. In a no-income-tax state the gap between them is smaller than the national rule assumes, and using net removes the guesswork entirely.
A workable ladder:
| Housing as share of take-home | On $150,000 in WA | What it means |
|---|---|---|
| Under 30% | Under $2,846/mo | Comfortable. Retirement, repairs and savings all fit. |
| 30–40% | $2,846–$3,794/mo | Normal for a first home. Workable with a real emergency fund. |
| 40–45% | $3,794–$4,269/mo | Tight. One job loss or major repair from trouble. |
| Over 45% | Over $4,269/mo | House-poor. Lenders will still approve this. |
Three adjustments the rule ignores entirely
Commute cost. Buying two counties out to save $80,000 looks smart until you add fuel, tolls, vehicle depreciation and ten hours a week. A cheaper house with a ninety-minute commute is often the more expensive choice in both money and life.
Your other debts. The 28% front-end ratio ignores them; the 45% back-end ratio is what actually gates approval. A $600 monthly car payment reduces what you can borrow by roughly $100,000 of purchase price. Pay down car loans before applying, not after.
What the house needs. Budget 1–2% of value annually for maintenance. On a $853,410 home that's $1,067 a month you should be setting aside and that no affordability rule includes. Older Washington housing stock, and our rain, make deferred maintenance expensive.
The number that actually matters
Not 28%, not 33%. It's what remains after the payment. If $9,486 comes in and the housing payment leaves you a few hundred dollars, the ratio is irrelevant — you cannot absorb a surprise, and houses are made of surprises.
The calculator shows the leftover figure directly, because it's the one worth watching.
Take-home estimates use 2026 federal brackets and FICA with the standard deduction and no retirement contributions. Your actual figure will differ.