U.S. e-commerce sales totaled $75.0 billion in the second quarter, up 4.9% from $71.5 billion in the first quarter of 2014, according to an estimate released today by the U.S. Commerce Department.

The estimate—adjusted for seasonal variation, but not for price changes—says e-commerce accounted for 6.4% of total retail spending in the quarter—a record high. That’s up from 6.2% in the first quarter and 5.8% in the second quarter of 2013. The Commerce Department includes purchases made from both PCs and mobile devices such as smartphones and tablets in its estimates.

On a year-over-year basis, e-commerce sales increased 15.7% on an adjusted basis from Q2 2014, while retail sales increased just 4.4% over the same period. Retail sales growth did make a slight rebound from the first quarter of 2014, when sales grew just 2.4% from the same quarter the previous year.

On a not-adjusted basis, the Commerce Department says e-commerce accounted for $70.1 billion of the $1.195 trillion in total retail spending during the first quarter, or 5.9% of total retail spending. Q2 2014 e-commerce sales increased 15.9% year over year on the not-adjusted basis, while total retail sales increased 4.8%.

Commerce Department estimates are based on a quarterly survey of about 12,500 U.S. merchants.

When further excluding sales of autos and fuel—products not commonly bought online—Internet Retailer calculates that e-commerce accounted for approximately 8.1% of total adjusted retail sales during the second quarter of 2014, up from 7.2% a year ago. On a non-adjusted basis, the same calculation shows e-commerce accounted for approximately 6.7% of total not-adjusted retail sales.