How this calculator works
A simple tote bag is two identical panels joined at the sides and base. Each panel is as wide as the finished bag plus a seam allowance on both sides. The height includes the seam allowances and, when the base is boxed, the depth: the extra fabric at the bottom folds into the base, and a square half the depth deep is removed from each bottom corner. The panels are cut across the fabric width, so the number that fit side by side decides how many rows of fabric the bag needs. Handles are long strips cut along the same length.
Formula
panel width = finished width + 2 x seam allowance. panel height = finished height + depth + 2 x seam allowance for a boxed base, or finished height + 2 x seam allowance for a flat bag. corner cut = depth / 2. fabric length = rows x panel height + 2 x handle length, where rows = 2 / panels across.
Worked example
A 30 cm wide, 35 cm high bag with a 10 cm base and a 1 cm seam allowance needs panels 32 cm wide and 47 cm high. Remove a 5 cm square from each bottom corner. Two panels fit across a 110 cm fabric in one row, so the fabric length is 2 x 47 = 94 cm, plus 120 cm for two 60 cm handles if you add them.
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Frequently asked questions
Why is half the depth removed at the corners?
Folding the bottom corners brings the front and back together to form the base. The seam at each corner is half the depth from the fold, so each cut-out square is half the finished depth on each side.
How much seam allowance should I use?
One centimetre is common for a tote, and 1.5 cm is easier for heavy canvas. Add more if you will finish the seams with a French seam or bind them, because that construction uses extra fabric.
Should I add interfacing?
Interfacing changes the feel but not the outer dimensions, so the cutting list stays the same. Cut interfacing from the same panel sizes, usually without seam allowance or with it removed after fusing, depending on the product.
What if the fabric is narrower than the panel?
The calculator rounds the number of panels across up to one, so it reports a fabric length for two panels stacked in rows. Join the panels with a seam down the side or centre and add the seam allowance for that join.