Seam Allowance

Cut open a side seam on any tee and there's a strip of fabric hidden between the stitching and the raw edge — that's the seam allowance. On lightweight jersey tee side seams it typically runs 1/4" to 3/8" (roughly 0.6 to 1 cm); heavier wovens, fleece, and denim commonly carry 1/2" to 5/8" allowances because thicker fabric needs more margin to keep the stitch line from pulling loose.

For anyone printing or embroidering, seam allowance quietly changes a garment's finished measurement without touching the pattern underneath it — two shirts cut from the identical die can measure a half inch apart in chest width depending on how much fabric the sewing operator takes up in that allowance. It also sets a hard limit on how close a full-width print can run to an edge: push a full-front graphic too near a side seam and the folded-under allowance can show through the ink or catch under the platen during the press. We've had a full-front proof come back visibly cropped because a factory quietly widened its standard allowance mid production run.

Pros check the seam allowance line on a spec sheet before locking an imprint area, not just the flat measurement chart, especially for oversized full-front art on wide-body blanks. If a design has to run edge-to-edge, get the supplier's standard allowance in writing and build in a buffer rather than trusting the chart alone.

Buyers often assume a size chart's chest measurement is taken before the seam allowance disappears into the stitch line — it isn't. That number is measured on the finished, already-sewn garment, with the allowance folded invisibly inside it, which is exactly why two "identical" blanks from different factories can print a hair differently even against a centered design.