Quilt Rag Quilt Calculator: Rag Quilt Blocks and Squares to Cut

Work out rag quilt blocks before you cut. Enter blocks across, blocks down, cut block size, seam allowance and layers per block, and see finished block size, finished quilt size, total blocks and total squares to cut, with the formula in steps.

Calculate your rag quilt

Blocks across

Blocks across is a whole number, greater than zero. Count blocks across one row of the quilt top.

Blocks down

Blocks down is a whole number, greater than zero. Count blocks down one column of the quilt top.

Cut block size in

Cut block size is the size of one square block as cut, before sewing, in inches or centimetres. This calculator assumes square blocks only.

Seam allowance in

Seam allowance is the wide exposed seam allowance for a rag quilt, usually 1 inch. It must be greater than zero and less than half the cut block size, otherwise the finished block would be zero or negative.

Layers per block

Layers per block is a whole number from 1 to 5. A rag quilt block is usually 3 layers: top, batting, backing.

Batting layer size

In a rag quilt with a batting middle layer, the batting is cut at finished size, so it stays inside the seams and does not show in the rag edge. Outer fabric layers are cut at cut size. Choose "All layers at cut size" only when your method cuts every layer the same size.

A rag quilt is made from square blocks sewn with a wide exposed seam allowance, usually 1 inch, which is then clipped and frayed to make the ragged edge. Each block is a stack of layers, usually 3: top, batting, backing. For bed fit first, use the Quilt Size Calculator, then this calculator for blocks.

Your result

Enter your measurements, then calculate.

How the calculator works

Step 1: Finished block size

Finished block size equals cut block size minus 2 times seam allowance, because each side of a block loses one seam allowance where it joins the next block. For cut block size 10 inches and seam allowance 1 inch, finished block size equals 10 minus 2 times 1, which is 10 minus 2, which is 8 inches.

Step 2: Finished quilt size

Finished quilt width equals blocks across times finished block size. For blocks across 5 and finished block size 8 inches, finished quilt width equals 5 times 8, which is 40 inches. Finished quilt length equals blocks down times finished block size. For blocks down 6 and finished block size 8 inches, finished quilt length equals 6 times 8, which is 48 inches.

Step 3: Total blocks and total squares to cut

Total blocks equals blocks across times blocks down. For blocks across 5 and blocks down 6, total blocks equals 5 times 6, which is 30 blocks. Total squares to cut equals total blocks times layers per block. For total blocks 30 and layers per block 3, total squares to cut equals 30 times 3, which is 90 squares. With the batting middle layer method, those 90 squares split into 60 fabric squares at cut size and 30 batting squares at finished size, because one layer per block is batting and the other two layers are fabric. With "All layers at cut size", all 90 squares are cut at cut size.

Assumptions, shown next to the result

This calculator assumes square blocks only, and seam allowance is the same on every side. By default, the batting middle layer is cut at finished size, so it stays inside the seams and does not show in the rag edge, while outer fabric layers are cut at cut size. Finished size is after sewing, before clipping and washing, because clipping and fraying do not change the sewn finished size in this calculation. If you want a finished quilt size first, work backwards with cut block size equals finished block size plus 2 times seam allowance, or use the Quilt Size Calculator for bed fit, then this calculator for blocks.

Rag quilt finished block size chart

This chart uses the same formula as the calculator, with seam allowance 1 inch: finished block size equals cut block size minus 2 times seam allowance. Layers per block do not change finished block size, so layers are not needed for this chart.

Cut block size	Seam allowance	Finished block size
8 inches	1 inch	6 inches
10 inches	1 inch	8 inches
12 inches	1 inch	10 inches

Chart values are a guide for the cut sizes shown. Your own cut block size or seam allowance may give a different result. Use the calculator above for your own measurements.

Worked example, checked against the calculator

Blocks across 5, blocks down 6, cut block size 10 inches, seam allowance 1 inch, layers per block 3.

Finished block size: 10 minus 2 times 1 equals 10 minus 2, which is 8 inches.

Finished quilt width: 5 times 8 equals 40 inches. Finished quilt length: 6 times 8 equals 48 inches.

Total blocks: 5 times 6 equals 30 blocks. Total squares to cut: 30 times 3 equals 90 squares. With the batting middle layer method: fabric squares 30 times 2 equals 60 squares at 10 inches, batting squares 30 times 1 equals 30 squares at 8 inches.

Frequently asked questions

What is a rag quilt?

How does seam allowance change finished block size?

Finished block size equals cut block size minus 2 times seam allowance, because each side of a block loses one seam allowance where it joins the next block. For example, cut block size 10 inches with seam allowance 1 inch gives finished block size 10 minus 2, which is 8 inches.

How many squares do I need to cut for a rag quilt?

Total blocks equals blocks across times blocks down, and total squares to cut equals total blocks times layers per block. For example, 5 blocks across and 6 blocks down give 30 blocks, and with 3 layers per block, total squares to cut equals 30 times 3, which is 90 squares.

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