Figuring property tax in King Co is no fun. Since WA has no income tax, a good portion of our taxes are levied through the property tax. This makes for lots of little "pieces" that have been added on separately. Within King County, your overall tax rate can run from about 7.3% up to about 11.9%, depending on what city / school district / fire district / water district / etc you live in. I'm including the link to the King County Assessor's web page that deals with property tax. I hope it will illuminate (not confuse!) the issues.
Jessica--The property taxes in this area are simply "way too high". Especially, I assume compared to Idaho. We do though live in a great area and I suppose that's just the price we pay. Wages are higher here and jobs are plentiful so hopefully that can balance out for you and we'll see you soon. Good Luck---Tom Berg Windermere, Woodinville Wa.
For lending purposes, we use 1.25% of the sales price to estimate taxes. Heather Cook is correct that taxes vary from area to area in King County depending on millage rates/levy codes. Whenever you buy a home, be prepared for your real estate taxes to be adjusted. Your sales price is an indicator to the tax assessor that the property may be worth more than it was last assessed (your taxes could go up).