Improvements to its mobile site and apps increased mobile conversion rates by 30% year over year through the three quarters ended Sept. 30, as other improvements to its e-commerce site also boosted conversions and sales, the company says.

The overall improvements contributed to a 17.3% increase in U.S. e-commerce sales through the first three quarters of this year, to $2.44 billion from $2.08 billion a year earlier, bringing online sales to 40.4% of total U.S. sales of $6.04 billion, Grainger says.

Customers using its mobile site and apps, for example, can now add products to a shopping cart and forward the cart to a supervisor to authorize the purchase. By expediting the purchase-approval process, this feature has contributed to a 50% year-over-year increase through the third quarter of 2015 in the number of customers who use its mobile apps, and a 30% increase in Grainger’s mobile conversion rate, says a spokesman for Grainger’s e-commerce team, which is headed by Paul Miller, vice president of global e-commerce, customer information and innovation.

About 18% of Grainger’s visitors on Grainger.com reach the site through its mobile apps, the spokesman adds. That amounts to about 846,000 monthly website visitors arriving from a mobile app, as Grainger.com attracts 4.7 million total monthly unique visitors according to web analytics firm SimilarWeb.

Grainger declines to specify its overall online conversion rate increase for its e-commerce site, but says it designed the improvements to its web site to better appeal to Grainger’s wide range of buyers, including those who like buying through the distributor’s paper catalog.

“A large portion of our customers are used to our physical catalog,” the spokesman says. “For these customers, the transition to the online world, where results are presented as long lists of products, is a distinct change, as they are used to seeing products grouped and presented a certain way.”  Grainger distributed about 1.5 million copies of its print catalog to its U.S. customers in 2015, featuring about 590,000 products across its categories of tools and equipment used in maintenance, repair and operations of office and industrial facilities. By comparison, its U.S. e-commerce site, Grainger.com, features a deeper selection of about 1.5 million products across those categories, the company says.

Earlier this year, Grainger’s in-house website developers launched a new “table” view for more than 1,400 product categories available to Grainger’s online business buyers. Now, when a customer clicks on a product type like “Lamps and Lamp Bulbs,” the site organizes items into side-by-side groups that display together such key attributes as price, brand or intended use. “The new table format facilitates quicker product comparison and selection” for Grainger.com users, the spokesman says. Grainger plans to expand the number of categories available through the table view through the end of 2015, he adds.

Developers at Grainger have also refined the distributor’s online search function. Instead of merely matching relevant products to search terms, as before, the new site search technology is designed to determine a customer’s intent and display a list of related products and research materials. “With more than 1 million products, spanning a wide variety of categories, it can be difficult for our customers to quickly find the right products to accomplish their tasks,” the spokesman says.

Grainger also consolidated this year the number of clicks customers take to check out. For example, Grainger now allows users to edit and save account data—such information as shipping address or payment information—so they don’t have to reenter that information for each order.

Grainger is ranked No. 34 in the new B2B E-Commerce 300, which lists companies by their annual B2B online sales.

Sign up for a free subscription to B2BecNews, a twice-weekly newsletter that covers technology and business trends in the growing B2B e-commerce industry. B2BecNews is published by Vertical Web Media LLC, which also publishes the monthly business magazine Internet Retailer. Follow Nona Tepper, associate editor for B2B e-commerce, on Twitter @ntepper90.