How to Convert the Size of a Quilt Block

By Contributing Writer ; Updated September 15, 2017

Things Needed

  • Graph paper
  • Pencil
  • Calculator
  • Ruler

You have found the perfect quilt block for a project. The problem is that the block pattern or the size of block pieces are either too big or too small for the size of the quilt you want to make. According to Minay Sirois, quilt designer for Black Cat Creations, you can convert the size of the quilt block with a few steps.

In this article, a "unit" means a square on the graph paper, and a "piece" means the piece of the block, which may be one or more units. For example, a square can be one unit and a rectangle can be two units.

Draw the pattern on graph paper. Each graph square should represent one logical unit of the pattern. According to Sirois, by drawing the block on graph paper and using it as a guide to resize the block, you keep the pieces in proportion to the new quilt block size.

To convert a quilt block, decide the desired, finished length and width of the block. Divide the width by the number of units in the first row to get the finished width of each unit. Divide the length by the number of units in the first column to get the finished length of each unit. If the finished piece is one unit, the width and length of the unit is the finished size of the piece. If the finished piece is more than one unit, add the width or length as appropriate to get the finished size.

To convert a block piece, assign the desired piece size to each unit of the pattern. Add each unit in the first row together to get the finished width of the block. Add each unit in the first column together to get the finished length of the block.


When converting the block size (not the piece size), be sure that each unit in the resized quilt block equals a measure found on your ruler. For example, your unit can be a size ending with a 7/8-inch, but should not end with a 1/16-inch. This will allow for precise measurements when cutting the fabric.

When cutting your pieces, remember to add a 1/4-inch to each side for the seam allowance.


There can be a mathetical problem depending on the size of the finished block and the number of units it includes. For example, a 12-inch square block that is made of 3x3 units cannot easily convert to an 8-inch block; each unit would be a 2 and 2/3-inch block. Your ruler does not include 2/3-inches, and you will not be able to cut precise pieces. In these situations, be flexible with the finished size. Instead of an 8-inch block, consider a 7 and 1/2-inch block and adjust your borders or sashing to get your desired, finished quilt size.