The Gartner survey suggests the number of these devices will increase 5.9 percent in 2013 to 2.35 billion, driven by sales in tablets, smartphones, and to a lesser extent, "ultramobile" PCs.
Traditional desk-based and notebook PC shipments are forecast to drop 10.6 percent to 305 million units, not including ultramobiles, a new category of PCs which includes smaller computers including convertible tablets.
Tablet shipments are expected to grow 67.9 percent to 202 million units, while the mobile phone market will grow 4.3 percent to 1.8 billion.
"Consumers want anytime-anywhere computing that allows them to consume and create content with ease, but also share and access that content from a different portfolio of products," said Carolina Milanesi, research vice president at Gartner.
"Mobility is paramount in both mature and emerging markets."
Sales of ultramobile PCs, which include the Google Chromebook, are expected to double in 2013 but remain at a relatively modest 20 million units, Gartner said.
Gartner said the red-hot growth in tablets and smartphones will taper off as these devices gain longer life cycles. The report said many consumers are opting for "basic" tablets to cut costs.
It said Apple's iPad mini represented 60 percent of overall Apple tablet sales in the first quarter of 2013.
"The increased availability of lower priced basic tablets, plus the value add shifting to software rather than hardware will result in the lifetimes of premium tablets extending as they remain active in the household for longer," said Gartner's Ranjit Atwal.
Lower-priced smartphones are also impacting the market, it found.
"Volume expectations for 2013 have been brought down as the life cycles lengthen as consumers wait for new models and lower prices to hit the market in the fall and holiday season," Atwal said.
"The challenge in the smartphone market is also that, as penetration moves more and more to the mass market, price points are lowering and in most cases so do margins."
Google's Android is expected to extend its dominance in 2013, accounting for 866 million devices, ahead of Microsoft Windows and Apple's iOS.
But Gartner said Apple is the most "homogeneous" with a large number of products in each segment, while Windows dominates in PCs and Android in smartphones.