SeeMyQuilt
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Four-at-a-time half-square triangle calculator

Sew around two squares, cut both diagonals, and get four half-square triangles. Enter the finished size.

Cut squares5 1/2"
  • 2 squares of each fabric make 8 units
  • Trim each unit to 3 1/2"
  • The outer edges are on the bias: handle gently and use starch

Four-at-a-time cutting chart

Finished sizeCut squaresTrim units to
1 1/2"3 3/8"2"
2"4 1/8"2 1/2"
2 1/2"4 3/4"3"
3"5 1/2"3 1/2"
3 1/2"6 1/4"4"
4"6 7/8"4 1/2"
5"8 3/8"5 1/2"

How it is calculated

Place two squares right sides together and sew 1/4" from the edge all the way around. Cut the square on both diagonals and press the four units open.

The side of each unit comes from the diagonal of the starting square, so the cut size is the unfinished unit divided by about 0.64. The calculator rounds up to the next 1/8" so there is a little to trim.

Questions

Why do these units stretch?

The outer edges are cut on the diagonal of the square, which is the bias of the fabric. Starch the squares before sewing and do not pull on the units when pressing.

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