Lesson 5 â Square in a Square
Lesson 5 – Square in a Square
Here’s the formula when you know the size of the center square and need to calculate the corner squares: Center square / 1.414, rounded up to the nearest 1/8 inch, + 7/8 inch (.875) = size of the outer squares. For example, let’s say the center square is 3 1/2″. 3.5 / 1.414 = 2.475 rounded up to 2.5 + .875 = 3.375 (or 3 3/8″)
Unfortunately, this math is backward. It tells you how to cut the triangles when you know the size of your center square. But most blocks are created at a specific size, so you need to know the measurements from the block in, not the center out. If you knew the size of the center square, you’d be able to calculate the outer squares for cutting the triangles. But how do you figure that? Well, it’s that same “magic” number: 1.414. Start with the “finished” sizes of the pieces. For example, say you want to make a square in a square that finishes at 12″. That means the block will be 12 1/2″ before you sew it into a quilt. Next, divide that finished size (12″) by 2. This gives you the finished length of the short sides of the triangles (in this case, 6″.) Next, you MULTIPLY by the magic number, 1.414. This tells you the approximate length of the long side of the triangles, which is the same as the measurement of the center square. In this case, that would be 8.484. That’s the finished size, so you need to add 1/2″ seam allowance for a total of 8.984. Round to 9″. Here’s the short version of how to calculate the size of the center square: Finished block size / 2 x 1.414 = Finished center square + .5 = Cut center square
Practice: Figure the cutting to make a square in a square block that finishes at 9”
Cutting size of Center Square:
Cutting size for corner squares:
Homework: Figure the cutting to make square in a square units that finish at 6” and 15”
Square in a Square Math Diagram
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Cut Center Square 9” Cut 2 side squares 7.25” and cut each in half once diagonally
Here’s the formula when you know the size of the center square and need to calculate the corner squares: Center square / 1.414, rounded up to the nearest 1/8 inch, + 7/8 inch (.875) = size of the outer squares. For example, let’s say the center square is 3 1/2″. 3.5 / 1.414 = 2.475 rounded up to 2.5 + .875 = 3.375 (or 3 3/8″)
Unfortunately, this math is backward. It tells you how to cut the triangles when you know the size of your center square. But most blocks are created at a specific size, so you need to know the measurements from the block in, not the center out. If you knew the size of the center square, you’d be able to calculate the outer squares for cutting the triangles. But how do you figure that? Well, it’s that same “magic” number: 1.414. Start with the “finished” sizes of the pieces. For example, say you want to make a square in a square that finishes at 12″. That means the block will be 12 1/2″ before you sew it into a quilt. Next, divide that finished size (12″) by 2. This gives you the finished length of the short sides of the triangles (in this case, 6″.) Next, you MULTIPLY by the magic number, 1.414. This tells you the approximate length of the long side of the triangles, which is the same as the measurement of the center square. In this case, that would be 8.484. That’s the finished size, so you need to add 1/2″ seam allowance for a total of 8.984. Round to 9″. Here’s the short version of how to calculate the size of the center square: Finished block size / 2 x 1.414 = Finished center square + .5 = Cut center square
Practice: Figure the cutting to make a square in a square block that finishes at 9”
Cutting size of Center Square:
Cutting size for corner squares:
Homework: Figure the cutting to make square in a square units that finish at 6” and 15”
Square in a Square Math Diagram
o o
Cut Center Square 9” Cut 2 side squares 7.25” and cut each in half once diagonally
