Quilt Block Size Calculator: Blocks and Layout for a Quilt Top

How the calculator works

Step 1: Blocks across and blocks down, nearest layout

Blocks across, nearest layout, equals target quilt width divided by block finished size, rounded to the nearest whole number. Blocks down, nearest layout, equals target quilt length divided by block finished size, rounded to the nearest whole number. For target width 60 inches and block size 12 inches, blocks across equals 60 divided by 12, equals 5 blocks, exactly. For target length 72 inches and block size 12 inches, blocks down equals 72 divided by 12, equals 6 blocks, exactly.

Step 2: Total blocks and finished quilt size, nearest layout

Total blocks equals blocks across times blocks down. For blocks across 5 and blocks down 6, total blocks equals 5 times 6, equals 30 blocks. Finished quilt width equals blocks across times block finished size. Finished quilt length equals blocks down times block finished size. For blocks across 5, blocks down 6 and block size 12 inches, finished quilt size equals 60 by 72 inches.

Step 3: Smaller layout and larger layout

Smaller layout rounds blocks across and blocks down down to whole numbers, and gives a smaller finished size than target size, unless target size is an exact multiple of block size. Larger layout rounds blocks across and blocks down up to whole numbers, and gives a larger finished size than target size, unless target size is an exact multiple of block size. For target 60 by 72 inches and block size 12 inches, smaller layout, larger layout and nearest layout are all the same, 5 by 6 blocks, because target size is an exact multiple of block size.

Assumptions, shown next to the result

Blocks are square, with no sashing between blocks, and no borders added. Block finished size is used as entered, with no seam allowance added, because finished size is already after seams are sewn. If you want sashing or borders, work out block layout first, then add sashing or borders with the Sashing Calculator or the Border Calculator.

Block layout chart

This chart uses the same formula as the calculator: blocks across and blocks down, nearest layout, equal target size divided by block size, rounded to the nearest whole number, total blocks equals blocks across times blocks down, finished size equals blocks times block size. Target quilt size is 60 by 72 inches for all rows.

Chart values are a guide for the block sizes shown. Your own target size and block size may give a different result. Use the calculator above for your own measurements.

Worked example, checked against the calculator

Target quilt size 65 by 80 inches, block finished size 12 inches.

Blocks across, nearest layout: 65 divided by 12 equals 5.42, rounded to the nearest whole number, equals 5 blocks. Blocks down, nearest layout: 80 divided by 12 equals 6.67, rounded to the nearest whole number, equals 7 blocks.

Total blocks, nearest layout: 5 times 7 equals 35 blocks.

Finished quilt size, nearest layout: 5 times 12 equals 60 inches wide, 7 times 12 equals 84 inches long, so finished quilt size equals 60 by 84 inches.

Smaller layout: blocks across 5, blocks down 6, total 30 blocks, finished size 60 by 72 inches. Larger layout: blocks across 6, blocks down 7, total 42 blocks, finished size 72 by 84 inches.

In this example, nearest layout finished width 60 inches is 5 inches smaller than target width 65 inches, and finished length 84 inches is 4 inches larger than target length 80 inches, because target size is not an exact multiple of block size. Add borders or sashing to reach target size, or choose the smaller or larger layout, if its finished size is closer to your target.

Frequently asked questions

Related calculators

Guide for this topic: How to Calculate Block Size.