T-Shirt Quilt Calculator

Interfacing is non-negotiable

Pellon SF101 on the back of every single panel, before you cut to size. This is the step that separates a professional t-shirt quilt from a wavy mess. Knit stretches in every direction — without interfacing, your blocks will distort as you sew and nothing will square up. Use a low iron temperature and a pressing cloth over the print side so you don't scorch the graphics. Once it's fused, the knit behaves like quilting cotton.

Cut all blocks the same size. Don't try to preserve every shirt's full graphic at the expense of uniform blocks. Measure the largest design across all your shirts, add seam allowance, and that's your block size. Smaller graphics get centered in the standard block. If a design is tiny, add a fabric frame around it rather than shrinking the block size.

Sashing between panels is almost always the right call. It frames each design, adds stability, hides minor size differences, and lets you hit your target quilt size without rounding up more shirts. Stick with a solid or low-contrast fabric — 2–3" width works well. This isn't the place for a busy print.