2 Inch Half Square Triangles: Cut Sizes for 2, 4 and 8 at a Time
For a 2 inch finished half square triangle, cut two 2 7/8 inch squares and use the two-at-a-time method, or cut 3 inch squares and trim. Before it is sewn into a block, the HST should measure 2 1/2 x 2 1/2 inches. Eight at a time uses 5 3/4 inch squares.
A half square triangle, or HST, is a square made of two right triangles sewn along the diagonal. It is the most common unit in quilting, used in pinwheels, sawtooth stars, bear paws and chevrons. Here is every cut size you need for HSTs that finish at 2 inches.
What size do you cut squares for 2 inch HSTs by each method?
"Exact" sizes give the finished HST with no trimming, if your seams are perfect. "Trim" sizes are a little larger so you can square each unit to 2 1/2 inches afterward, which most quilters prefer.
| Method | Exact cut | Cut to trim | HSTs per pair | Yards of each fabric for 100 |
|---|---|---|---|---|
| Two at a time (draw a diagonal, sew both sides) | 2 7/8 in | 3 in | 2 | 3/8 yd |
| Four at a time (sew around the square) | 4 1/8 in | 4 1/2 in | 4 | 1/2 yd |
| Eight at a time (magic eight) | 5 3/4 in | 6 in | 8 | 1/2 yd |
Trim to the unfinished size
Every 2 inch HST should be squared to 2 1/2 inches. Line up the 45 degree line of a square ruler with the seam, trim two sides, rotate, and trim the other two.
Which blocks use 2 inch half square triangles?
HSTs fit block grids exactly. Multiply the finished HST size by the number of units across the block.
| Grid | Finished block | Example blocks |
|---|---|---|
| 2 x 2 | 4 in | Pinwheel, broken dishes |
| 3 x 3 | 6 in | Shoo fly, churn dash variation |
| 4 x 4 | 8 in | Sawtooth star, flying geese star, Ohio star variation |
| 5 x 5 | 10 in | Bear paw variation, 25 patch stars |
| 6 x 6 | 12 in | Large star medallions, pieced medallions |
Can you cut 2 inch HSTs from precut fabric?
| Precut | Two at a time | Eight at a time |
|---|---|---|
| Mini charm (2 1/2 in) | Too small | Too small |
| Charm pack (5 in) | Yes | Too small |
| Layer cake (10 in) | Yes | Yes |
Tools for accurate 2 inch HSTs
Bloc Loc Half-Square Triangle Ruler Set #2
$72.75A slotted ruler that locks onto the seam so every HST trims to size with sharp points.
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Olfa 17 x 17 Rotating Cutting Mat RM-17S
$100.98Turn the mat, not the HST, when trimming all four sides of dozens of units.
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Olfa 45mm Quick-Change Rotary Cutter RTY-2/C
$14.28A precise 45 mm cutter for trimming small units cleanly.
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Frequently asked questions
What size square do I cut for a 2 inch half square triangle?
For the two-at-a-time method, add 7/8 inch to the finished size: cut 2 7/8 inch squares. Many quilters add a full inch instead, cutting 3 inch squares, then trim each HST to 2 1/2 inches for perfectly sharp points. Trimming wastes a little fabric but forgives slightly wobbly seams.
What size is a 2 inch HST before it is sewn into a block?
The unfinished size is 2 1/2 x 2 1/2 inches: the 2 inch finished size plus a 1/4 inch seam allowance on each side. Square every HST to that size with a small square ruler, lining the ruler's diagonal line up with the seam, before sewing it to other units.
How do I make eight 2 inch HSTs at once?
Cut two 5 3/4 inch squares (or 6 inches to trim). Place them right sides together, draw both diagonals, and sew 1/4 inch on each side of both lines. Cut vertically and horizontally through the center, then along both drawn lines, and press open. You get eight HSTs to trim to 2 1/2 inches.
Can I make 2 inch HSTs from a charm pack?
Yes. A 5 inch charm square is big enough for two-at-a-time HSTs that finish at 2 inches, since you only need 2 7/8 inch squares. Pair a light and a dark charm, sew on both sides of the diagonal, and cut apart. A 42 piece charm pack makes up to 42 HSTs this way when paired with 21 contrasting squares.
How much fabric do I need for 100 2 inch HSTs?
Using two at a time with trimming, you need 50 squares of each of two fabrics cut at 3 inches, which is 3/8 yards of each fabric from 42 inch cotton. Eight at a time is more efficient to cut: 13 squares of each fabric at 6 inches, or 1/2 yards of each.
How we research: we compare manufacturer specifications, owner manuals, published standards and recurring themes in verified owner reviews. We do not test products in person, and this is researched guidance, not professional advice. Follow your machine manual and pattern, and take care with rotary cutters, hot irons and needles. As an Amazon Associate we earn from qualifying purchases.