With just seven shopping days until Christmas, upbeat US consumers are spending their way to the best retail holiday shopping season in seven years.

But shoppers will have to sprint to the finish for retailers to really celebrate a great end-of-year finish.

Last year, Christmas week was the biggest sales week of the season — topping even Black Friday’s Thanksgiving week, according to the National Retail Federation.

But this year consumers, buoyed by low unemployment, sky-high stock performances and the expectation that a tax increase will put more money in their pockets, are showing signs that the stepped-up spending has staying power.

Sales through the first half of December were so strong across the board — for both online and brick-and-mortar retailers — that many prognosticators increased their forecast for holiday spending.

“For the first time in about a dozen years we are seeing people in all income categories spending more money this year,” said Craig Johnson, president of Customer Growth Partners, which has raised its holiday forecast to 5.6 percent from 4.3 percent based on research his firm conducts at some 90 malls across the country.

Twice as many consumers are buying gifts in the $50 range this year compared with about $25 last year, according to Britt Beamer, chairman of America’s Research Group, which tracks consumer spending.

Spending growth rates are on track to be the highest since 2010, according to MasterCard SpendingPulse, which tracked retail spending, capturing cash, check and credit card transactions at both small and large retailers, through Dec. 9, showing that spending is up 3.6 percent during the period.

MasterCard forecasts holiday spending through Dec. 31 could surpass 5 percent growth.

“No recent year has seen spending rise by more than 4 percent,” said MasterCard’s Sarah Quinlan.

Investors are feeling bullish as well.

Shares of Macy’s are up 3.2 percent in December through Friday — the first time the retailer’s shares have risen over that period since 2009.

At Kohl’s, shares this month are up 7 percent, only its third positive December since 2008, when its stock rose 19.8 percent over the same period.

So what are Americans buying?

Shoppers, it turns out, are feathering their nests with anything that gussies up their homes. Home improvement spending is up 11.6 percent — representing the biggest hike in all categories — through early December, according to MasterCard.

“We have seen very strong home improvement spending all year, but there’s been a surge during the holiday season,” Quinlan told The Post. “People are giving new comforters, sheets and sofas or anything that enhances home life.”

Other categories showing strong sales increases are travel, electronics, phones and videos games.

While apparel sales overall have been weak and are generating the highest discounts — up to 50 percent off — women’s yoga pants have been a runaway hit during the holidays, according to MasterCard.