Millions of U.S. workers will see increased pay in 2019 due to minimum-wage hikes in 20 states and 21 cities.

With the federal minimum wage stuck at $7.25 an hour since 2009, many states and cities have taken it upon themselves to raise the rate for the lowest-paid workers.

Eight states — Arizona, California, Colorado, Maine, Massachusetts, Missouri, New York, and Washington state — are phasing in increases that will eventually put their minimum wages at $12 to $15 an hour, according to the National Employment Law Project (NELP), a nonprofit that advocates for higher minimum wages.

In addition, 13 cities and counties are hiking their minimum wages to $15 an hour or higher in the new year, the nonprofit says.

Workers in lower-cost areas will benefit the most from the increases, said Paul Sonn, state program policy director at NELP. The change will mean less for people in high-cost states like California and New York.

"Right now, in an expensive state like California, a single worker needs about $20 an hour to afford the basics," Sonn said. "Whereas $15 is what a single worker needs in a less expensive state such as Alabama, Florida or Texas."

"Fifteen dollars an hour has become the new minimum wage, meaning that that’s to afford the basics," he said. "It’s just a start. Those with children and in expensive states need even more."

Currently, 29 states and the District of Columbia have minimum wages above the federal minimum wage of $7.25 per hour. The federal minimum for workers who receive tips is $2.13 per hour.

The states raising the minimum wage in 2019 are: Alaska, Arizona, Arkansas, California, Colorado, Delaware, Florida, Maine, Massachusetts, Michigan, Minnesota, Missouri, Montana, New Jersey, New York, Ohio, Rhode Island, South Dakota, Washington and Vermont, according to NELP.

Over the course of the new year, more than 17 million workers will see a raise from the higher minimum wages, NELP said.