How to Do the Math to Cut out 8 Half Square Triangles
We have been asked a number of times, how to calculate the size of the starting pieces of fabric when you want to cut 8 Half Square Triangles at the one time. So here it is. We also have a video below on how to cut the 8 half square triangles.
Calculation to work out the size of the starting fabric:
The size of your finished block + 7/8″) x 2 = size of starting fabric
For example if you want your finished block to be 2 1/2″ your calculation will be:
- (2 ½” + 7/8″) x 2 = 6 ¾” (we round up to 7″ – see note below)
So the size of the square that you need to start with is 6 ¾”
This will result in 8 unfinished squares that are 3″ each. When you sew them into the project you will be using a ¼” seam which will bring the size of the block down to a finished size of 2½”.
In the following video, we show you how to cut half-square triangles. One of these methods is the ‘How to Cut 8 Half Square Triangles’ technique. It’s a great way of cutting lots of half-square triangles quickly.
Scroll through to the 5-minute mark for the information on cutting 8 half square triangles.
Anne Pimenta says
Love this video – especially your detailed instructions,
Alanda Craft says
Thank you Anne. So glad we could help.
Pam White says
Thank you! No one Explains this!
Alanda Craft says
Very happy to hear that our tutorial helped Pam 🙂
Ana says
Hola quisiera saber cómo calcular el cuadrado grande si quiero cuadrado final, por ejemplo 3,”,6″,8″, etc es decir como cálculo el cuadrado grande
Robert McCalman says
I made two of these quilts and was very pleased with with both sold one and kept one it is one of my favorites
Uschi says
Your video is very helpful.. Thank you so much Alanda
Alanda Craft says
You are most welcome, happy to hear that the tutorial was helpful. 😊