Sewing & Quilting Math: Cutting Sizes, Seam Allowances, Fabric Yardage, Binding & Size Grading

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Turn block size, blocks across and down, sashing and borders into the finished width and length of four quilts, then work backwards: how many blocks across reach a target width.
• Find the cut size of every piece in a block from its finished size and shape: a lookup of the add-on, finished + add-on, the units for the whole quilt and the squares to cut when one square makes two or four triangles.
• Work out how much of each fabric to buy: whole pieces per strip with INT, strips with ROUNDUP, fabric length, yards rounded up to 1/8 with CEILING and the same in metres.
• Calculate the binding strips from the quilt's perimeter, the fabric they need, and the backing for two seam layouts, then buy the one that uses less fabric.
• Pick sizes from a fictional size chart with an approximate XLOOKUP, cut the larger of the bust and hip sizes, add ease for the chosen fit and turn the finished bust into the width of a front pattern piece.
• Grade a pattern for a customer whose bust and hip fall between sizes: find the lower size with MATCH, the fraction towards the next size, and the interpolated pattern widths at the bust and the hip.
• Draft full, half and quarter circle skirts: the waist radius from the waist measurement with PI, the outer radius including the hem allowance, and the length of the hem you will have to sew.
• Match every project need against your fabric stash with SUMIFS on type and colour, buy only what is missing in 10 cm steps, cost the shopping list and total it for one project.