Grunff wrote:

Yup, same sizes, at least from a builders merchant. Most sheds will
carry 2", 4" and 6", not sure about 8" and 10". I haven't been too
impressed with softwood bought from sheds, and usually prefer a builders
merchant.

By the time you're up to 8", and fer sure 12" (I know the OP asked about
10" but I've not seen it about) you're as well to go for laminated
board, usually called "pineboard" over here (at least down in Bristol
;-). It's long strips of pine, each about 2" wide, glued firmly together
to form boards of "arbitrary" width - common ones seem to be 6", 8",
12", 18", 24" (masquerading as metric sizes of 150mm, 200mm, 300mm,
450mm, and 600mm respectively), all at the "usual" nominal thickness of
18mm-that's-3/4". In some editions the corners are very slightly
bevelled off.

By using laminated board, your shelves are usefully less prone to
cupping - in theory they alternate the grain direction in alternate
strips, though looking at the end grain of the multiple shelves in my
study the best that can be said for this batch is "the grain doesn't run
the same way in adjacent strips very often"! It's also cheaper than the
wider planks of one-piece wood, as you can make it from (quarter-sawn
bits of - as if!) smaller-trunked trees.

HTH - Stefek