But when you use a quilt ruler to cut squares and triangles, you can't just add 1/4" to the strip.
Seam Allowance Story
A 1/4" seam allowance is most commonly used in quilting.
To make Squares, you need to add ½":
To make Half or Quarter Square Triangles,
you need to cut Squares first.
Then, cut them diagonally in half or in quarters.
If you only add 1/2", you won't have any seam allowances on the diagonal edges.
So, these are the seam allowance amounts patterns use today:
But Those Amounts
are not Exactly Right!
Ever Wondered Why
you have to trim your triangle squares down to the right size?
Triangles come out slightly larger than squares.
You Might be Surprised
to hear that you can't add the precise amounts of seam allowances for triangles, using a quilt ruler alone.
That's because rulers only have lines every ⅛”.
- 7/8" is almost 1/32" too much for HSTs
- 1¼" is almost 1/16" too much for QSTs
This is why many quilters today add even more
and then trim them down to the right size later.
Believe it or not, the exact amounts are:
You could use individual templates or
dies to cut perfect triangles.
But you'll need a separate template or die for each size you want to cut.
And that can get really expensive!
Cut accurate triangles
Any Size! No Expensive Dies!
Seam Allowance Additions
let you add the precise amounts of seam allowance
for triangles right on the edge of the ruler.
The purple S Addition
adds ½" for squares.
The Green H Addition
adds 0.854" for HSTs.
The Red Q Addition
adds 1.207" for QSTs.
When you add the accurate seam allowance amounts, your squares and triangles will match perfectly.
▶️
Ever Wondered Why
you have to trim your triangle squares down to the right size?
Triangles come out slightly larger than squares.
You Might be Surprised to hear that you can't add the precise amounts of seam allowances for triangles, using a quilt ruler alone.
That's because rulers only
have lines every ⅛”.
- 7/8" is almost 1/32" too much for Half Square Triangles
- 1¼" is almost 1/16" too much for Quarter Square Triangles
This is why many quilters today add even more and then trim them down to the right size later.
Believe it or not, the exact amounts are:
You could use individual templates or dies to cut perfect triangles.
But you'll need a separate template or die for each size you want to cut.
And that can get really expensive!
Cut accurate triangles
Any Size!
No Expensive Dies.
Seam Allowance Additions
let you add the precise amounts of seam allowance for triangles right on the edge of the ruler.
The Green H Addition
adds 0.854" for HSTs.
The Red Q Addition
adds 1.207" for QSTs.
When you add the accurate seam allowance amounts, your squares and triangles will match perfectly.
The Most Economical Way to Make
Accurate Quilt Blocks in Any Size:
The Super Easy
Finished-Size Quilting Set
Make Any Blocks As You Envisioned
No Templates or Dies / Left-Handed Friendly
- Successful Projects Guaranteed!
Free US Shipping
Sold out
Using the same set, you can also
make all the blocks below.
All you need is your rulers and our FSQ Set.
For the best results, we recommend the Super Easy FSQ Set, but if you already have some of the tools, individual tools are available here:
Seam Allowance Additions:
Automatically add the exact seam allowances.
Come with an 8-page booklet that
includes the Quilt Block Breakdowns.
You can also purchase an extra copy separately.
Sold out
Guidelines4Quilting
© 2025 Guidelines4Quilting All rights reserved.
