What size is a fat quarter?

A fat quarter is approximately 50 x 56cm (18 x 22in). It is made by cutting a half-metre of 112cm-wide fabric in half along the fold, giving a squarer piece than a regular quarter metre.

What is the difference between a fat quarter and a long quarter?

A fat quarter is 50x56cm (wider, shorter). A long quarter is 25x112cm (narrow, full width). Fat quarters are better for cutting larger pieces; long quarters suit strips and borders.

How many 12.5cm squares can I cut from a fat quarter?

With the default 1cm trimming allowance the tool fits 3 across × 4 down = 12 squares at 12.5cm (5in) each — matching the widely quoted "12 charm squares per fat quarter". Set the trimming allowance to 0cm and you get the textbook 4 × 4 = 16, but in practice the selvedge and uneven raw edges need squaring up first, so 12 is the realistic yield. A 12.5cm cut square gives an 11.2cm (4½in) finished charm square after a ¼in seam allowance on each side.

Should I pre-wash fat quarters?

For quilting, most quilters do not pre-wash. The slight shrinkage after washing gives a lovely crinkled look. If mixing with pre-washed fabrics or if the fabric bleeds colour, pre-wash and press before cutting.

Fat Quarter Calculator — Free Quilting Tool

How We Calculate This

The calculator first trims the raw edges off the fat quarter, then determines how many pieces fit across the usable width and down the usable height, and finally works out how many fat quarters you need.

The formula

Usable width = FQ width − Trimming allowance

Usable height = FQ height − Trimming allowance

Pieces across = floor(Usable width ÷ Piece width)

Pieces down = floor(Usable height ÷ Piece height)

Pieces per FQ = Across × Down

Fat quarters needed = ceil((Total pieces × (1 + waste %)) ÷ Pieces per FQ)

With the default 1cm trimming allowance, a 50×56cm fat quarter has a 49×55cm usable area, so 12.5cm squares give floor(49 ÷ 12.5) = 3 across and floor(55 ÷ 12.5) = 4 down = 12 squares. Set the trimming allowance to 0cm for the no-waste theoretical maximum.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before cutting or purchasing fabric.

Fat Quarter Calculator — Pieces From Fat Quarters