The cost of living varies considerably across the US, and while some households are struggling to make ends meet, others have a small fortune left over after they've covered the necessities.

To find out where Americans have the most and least disposable income, SmartAsset subtracted essential expenses from the median yearly household income in 100 of the country's biggest counties. Costs for both single adult households and those with two adults and one child were calculated.

Households in Fairfax County, Virginia, had the most disposable income overall. A family of two adults and one child could have as much as $29,941 to play with after covering the year's essential costs, while a single adult on the same median income could have $83,875 left over.

There are four other counties where the median disposable income for a single adult household exceeds $70,000: Santa Clara County, California ($81,883), Nassau County, New York ($77,600), San Francisco County, California ($75,587), and San Mateo County, California ($72,264).

After Fairfax County, small families have the most disposable income in Collin County, Texas ($20,801) and Santa Clara County, California ($20,377).

Via SmartAsset.

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