What does WatchPennies calculate?

WatchPennies estimates cost of living by US county across housing, food, transportation, healthcare, childcare, other necessities, taxes, and income context.

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Can I compare two counties on WatchPennies?

Yes. WatchPennies lets you compare counties and adjust salary and family type to estimate relative cost differences.

What does the King County, WA vs San Mateo County, CA comparison show?

It compares estimated living costs by category, including housing, food, transportation, healthcare, childcare, other necessities, taxes, and income context.

Can I change the salary and family type?

Yes. The comparison calculator supports salary and family type inputs so you can model costs for different households.

Does WatchPennies require an account for comparisons?

No. County comparisons are available without creating an account.

King County, WA vs San Mateo County, CA: Cost of Living Difference

Is it cheaper?

King County, WA is cheaper than San Mateo County, CA.

Moving to San Mateo County, CA is estimated to cost $20,263 more per year.

Cheaper County

King County, WASpend $20,263 more per year.

Salary needed

$50,000 in King County, WA is about $63,795 in San Mateo County, CA.

Biggest drivers

Taxes increases by $10,713 per year. No measured category is cheaper in San Mateo County, CA.

Housing: $3,020 higher in San Mateo County, CA

Taxes: $10,713 higher in San Mateo County, CA

Childcare: about the same in both counties

Healthcare: $2,735 higher in San Mateo County, CA

Food: $185 higher in San Mateo County, CA

Transport: $2,617 higher in San Mateo County, CA

King County, WA→San Mateo County, CA

Equivalent salary in San Mateo County, CA

$63,795

+27.59% higher

Current salary: $50,000

Household: 1 adult · 0 children

Median Income in King County, WA: $154,490

Median Income in San Mateo County, CA: $184,583

Living Index in King County, WA 47.55%

Living Index in San Mateo County, CA 50.77%

This estimate matches your purchasing power (equivalent salary) when moving from King County, WA to San Mateo County, CA.

* Living index is estimated as (estimated total cost / area median income) * 100. A living index above 100% means modeled costs exceed median income.

Cost of Living Breakdown by Category

Summary

Moving from King County, WA to San Mateo County, CA is estimated to cost $20,263 more per year. To maintain similar purchasing power, a $50,000 salary in King County, WA would need to be about $63,795 in San Mateo County, CA. The biggest increase is taxes, followed by housing.

This is a 27.59% increase in modeled annual costs. Taxes is $10,713 per year higher (74.71%); Housing is $3,020 per year higher (11.04%).

Below we break down the annual categories behind the difference using Economic Policy Institute 2026 Family Budget data.

What changed the most?

The following cards show the annual category differences that most affect the move to San Mateo County, CA.

Biggest Cost

Largest annual cost increase when moving to San Mateo County, CA

Annual Increase:

$10,713 per year

TAXES has the largest annual increase when moving to San Mateo County, CA.

Biggest Savings

Largest annual savings when moving to San Mateo County, CA

Annual Savings:

No savings

No measured category is cheaper in San Mateo County, CA.

Breakdown of price percentages per category.

Numbers are average costs per section.

Category	Difference
Housing	11.04% higher
King County, WA San Mateo County, CA Average Cost $27361.00 $30381.00 INFO: Housing costs are based on Department of Housing and Urban Development data. The estimate uses 40th percentile rent for privately owned rental units in each area. Studio apartments are paired with one-adult households, one-bedroom apartments with two-adult households, and two-bedroom apartments with households that have children.
Food	3.58% higher
King County, WA San Mateo County, CA Average Cost $5169.00 $5354.00 INFO: Food costs are based on the U.S. Department of Agriculture's food plans. Numbers are normalized to each area using Feeding America and Meal Gap data. This estimate assumes most food is bought at local grocery stores and prepared at home.
Transport	22.40% higher
King County, WA San Mateo County, CA Average Cost $11684.00 $14301.00 INFO: Transportation costs are a combination of auto ownership, auto use, and public transit. Data is collected from the Center for Neighborhood Technology (CNT).
Healthcare	56.98% higher
King County, WA San Mateo County, CA Average Cost $4800.00 $7535.00 INFO: Healthcare expenses come from average insurance premiums and out-of-pocket costs. The estimate assumes families purchase the lowest-cost available insurance plan under the Affordable Care Act. Data comes from Kaiser Family Foundation and the U.S. Department of Health and Human Services (HHS).
Other Costs	9.85% higher
King County, WA San Mateo County, CA Average Cost $10100.00 $11095.00 INFO: This cost is calculated through the average spending of categories deemed necessary by the Bureau of Labor Statistics Consumer Expenditure Survey. These include apparel, personal care, household supplies, reading materials, and school supplies.
Childcare	0.00% higher
King County, WA San Mateo County, CA Average Cost $0.00 $0.00 INFO: Childcare expenses are based on combined costs for center-based care and family-based care for 4-year-olds and school-aged children. For households with one child, the estimate assumes the child is 4 years old. For households with two children, the estimate assumes the second child is 8 years old.
Taxes	74.71% higher
King County, WA San Mateo County, CA Average Cost $14340.00 $25053.00 INFO: Taxes are calculated from the National Bureau of Economic Research. The number weighs in personal income tax, state income tax, federal Social Security, and Medicare taxes.

In San Mateo County, CA, modeled annual costs are $93,718 compared with $73,455 in King County, WA.

Overall, annual costs are higher in San Mateo County, CA. The category breakdown above shows whether housing, taxes, transportation, healthcare, food, childcare, or other necessities are driving the increase.

In this case San Mateo County, CA and King County, WA are both metropolitan locations.

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