HST Calculator 🔺
Calculate exact cutting sizes for Half-Square Triangle (HST) units. Supports 2-at-a-time, 4-at-a-time, and 8-at-a-time methods with seam allowance included.
How to Use the HST Calculator
Enter the finished size of your Half-Square Triangle (HST) — this is the size after sewing and pressing, not including seam allowance. Select your preferred cutting method (2-at-a-time, 4-at-a-time, or 8-at-a-time).
The 2-at-a-time method is the simplest: cut two squares, draw a diagonal, sew 1/4" on both sides, cut apart. The 4-at-a-time and 8-at-a-time methods are more efficient for large quantities.
The calculated cutting size includes the seam allowance. Always press your HSTs carefully and square them up to the exact finished size for precise piecing.
Frequently Asked Questions
What is a Half-Square Triangle (HST)?
A Half-Square Triangle (HST) is one of the most fundamental quilt blocks, made by sewing two squares of fabric together diagonally to create two triangle units. HSTs are used in countless quilt patterns including pinwheels, stars, and chevrons.
How do I calculate the cutting size for HSTs?
For the 2-at-a-time method, add 7/8" to the finished HST size. For the 4-at-a-time (quartered-square) method, multiply the finished size by √2 and add 1.25" (bias seam allowance), then round to the nearest 1/8". For the 8-at-a-time method, add 7/8" to the finished size and multiply by 2 (= finished × 2 + 1.75"). QuiltMetric calculates all three methods automatically.
What is the most efficient HST method?
The 8-at-a-time method is the most efficient, producing 8 HSTs from just 2 squares with minimal fabric waste. The 4-at-a-time method is also popular. The 2-at-a-time method is the simplest but least efficient.
Why is my HST not the right size after sewing?
HSTs often come out slightly larger than expected. Always sew with a precise 1/4" seam allowance and press seams carefully. Trim HSTs to the exact finished size + 1/2" (for seam allowances) using a square ruler before incorporating them into your quilt.
How can I contact QuiltMetric for support?
For questions or support, you can reach us at card.workshop@gmail.com. We aim to respond within 1-2 business days.