How large can/should I print when designing t-shirts?

Standard sizes of heat transfer paper include 8.5" x 11" (Letter) and 11" x 17" (Tabloid), but we also offer rolls and European sizes such as A3 and A4 on select papers. Not all printers can print up to 11" x 17" however, so do check with the manufacturer or distributor on maximum print sizes. Would 8.5" x 11" be large enough for your business? Look into the sizes of shirts you're most likely to sell -- this size would work perfectly for children's wear to an adult size small or medium, but you may need a larger size to accommodate large or extra-large shirts.