Mercer Island vs Sammamish: Comparing Seattle's Top Suburbs

According to NeighborScore's composite index, Mercer Island and Sammamish are the two highest-scoring suburbs in the greater Seattle area, and the two nearly tie: Mercer Island's 98040 posts a 92, while Sammamish's 98074 and 98075 post a 93 and a 92. Every one of the three ZIPs beats Washington's statewide average overall score of roughly 62 by a wide margin. The real split between the two cities shows up not in safety or schools, where both dominate, but in home prices, where Mercer Island costs nearly 900 thousand dollars more than Sammamish for a comparable composite score.

Both suburbs sit in King County and share the same Puget Sound commuter appeal, but they draw different kinds of buyers. Mercer Island trades on a small, dense island footprint with direct light-rail access into downtown Seattle. Sammamish spreads across two ZIP codes east of Lake Sammamish with newer, larger subdivisions and a straight shot to the Eastside tech corridor. This piece uses NeighborScore's own crime, school, and value data for all three ZIPs to settle the comparison on numbers rather than reputation.

How the NeighborScore composite works

NeighborScore's composite index scores every ZIP code from 0 to 100 using the formula overall_score = crime_score × 0.53 + school_score × 0.47 — safety and school quality only. Affordability, tracked separately as the value_score, is displayed on every ZIP profile for context but is not part of the overall score. A high overall score means low crime and strong schools; it says nothing about whether a ZIP is cheap or expensive to buy into, which is why this comparison treats price as its own category.

Mercer Island's 98040 scores a 95 on crime and an 89 on schools, combining to a 92 overall. Sammamish's 98074 scores a 95 on crime and a 90 on schools for a 93 overall, edging out Mercer Island by one point and holding the highest composite of the three ZIPs compared here. Sammamish's second ZIP, 98075, scores an identical 95 on crime with an 89 on schools, landing at 92 overall — tied with Mercer Island. In practical terms, all three ZIPs are functionally elite on safety and academics, and the gap between a 92 and a 93 will not change a family's day-to-day experience.

Comparing Mercer Island and Sammamish ZIP codes by score

1. 98074, Sammamish — overall 93 (crime 95, school 90)
2. 98040, Mercer Island — overall 92 (crime 95, school 89)
3. 98075, Sammamish — overall 92 (crime 95, school 89)

School quality at this level comes down to specific campuses rather than the city label. In 98040, Lakeridge Elementary posts 89 percent math and 91 percent reading proficiency, and Mercer Island High School reaches 86 percent math and 95 percent reading, among the strongest combined marks in the state. In 98074, Samantha Smith Elementary leads with 91 percent math proficiency, and Eastlake High School posts 94 percent reading proficiency across nearly 2,500 students. In 98075, Skyline High School matches that 94 percent reading rate for an even larger student body, though Sunny Hills Elementary trails the ZIP average at 79 percent in both subjects. NCES assessment data shows Sammamish's larger school district gives it more high-performing individual campuses, even though its ZIP-level school score sits a point or two from Mercer Island's.

Home prices and affordability: where the suburbs diverge

The scores converge, but the price tags do not. Zillow's ZHVI data for these three ZIPs shows Mercer Island's 98040 at a median home price of roughly 2.49 million dollars as of April 2026, up 9.1 percent from two years earlier. Sammamish's 98074 sits far lower at about 1.65 million dollars, up a modest 2.1 percent over the same period, and 98075 has actually pulled back to roughly 1.78 million dollars, down 3.3 percent from its 2024 level. That means Mercer Island now costs about 51 percent more than 98074 and roughly 40 percent more than 98075 for a nearly identical safety-and-school composite.

Every ZIP here still runs well below the Washington state average value_score of about 52, meaning all three are pricier than a typical Washington ZIP relative to income — Mercer Island's 98040 posts the lowest value_score of the group at 17, versus 22 in Sammamish's 98074 and 20 in 98075, so Sammamish is the comparatively more affordable choice of the two cities even though neither is cheap. Household income tells a similar story in reverse: Sammamish residents report a higher median income in both ZIPs (244,362 dollars in 98074 and 250,001 dollars in 98075) than Mercer Island's 219,069 dollars, and homeownership runs higher too, at 84 and 87 percent in Sammamish versus 67 percent on Mercer Island, where more of the housing stock is rented. Buyers who want the same score for less capital outlay should start their search in Sammamish rather than Mercer Island.

According to the FBI Crime Data Explorer, both cities also report violent crime rates well under the King County average, which is consistent with the 95-point crime scores both ZIPs share — neither city has a meaningful edge on safety once the data is normalized to population.

For a wider look at how other high-scoring Western metros stack up against each other, NeighborScore's full guide to comparing sunbelt and coastal metros is available on the blog.

Bottom Line

Sammamish's 98074 edges out Mercer Island's 98040 on the NeighborScore composite, 93 to 92, and does it at roughly two-thirds of the price. Mercer Island still wins on light-rail access to downtown Seattle and a marginally higher reading proficiency at the high school level, but buyers optimizing purely for the data get more house, more income headroom, and a nearly identical safety-and-school score by choosing Sammamish.