Calculator
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Where the numbers come from
Piecing: seam length times a lockstitch ratio
The thread company Coats publishes thread consumption ratios for each stitch type. For a 301 lockstitch, the stitch every home sewing machine makes, its thread consumption guide gives 2.5 centimeters of thread per centimeter of seam, half from the needle and half from the bobbin, and adds 10 to 15% for waste (thread breaks, tails, rethreading). The ratio is the same in inches. The calculator uses 2.5 and 15%.
The seam length comes from your quilt size and typical piece size, treating the top as a grid of squares:
| Step | Formula | 60 × 72 quilt, 3 in pieces |
|---|---|---|
| Pieces across and down | width ÷ piece, length ÷ piece | 20 × 24 |
| Seams within rows | (across − 1) × length | 19 × 72 = 1,368 in |
| Seams joining rows | (down − 1) × width | 23 × 60 = 1,380 in |
| Binding seam | 2 × (width + length) + 10 | 274 in |
| Thread | total seams × 2.5 × 1.15 ÷ 36 | 3,022 × 2.875 ÷ 36 = 241 yd |
Real blocks have triangles and diagonal seams, and some pieces are smaller than others, so pick the piece size that's typical and treat the result as approximate.
Free-motion and edge-to-edge quilting: Superior Threads' averages
Superior Threads publishes average top-thread use by quilt size and density, based on its staff's experience: 200, 400 and 600 yards (light, medium, heavy) for a lap or crib quilt; 400, 800 and 1,200 for a twin; 600, 1,000 and 1,600 for a queen; 750, 1,500 and 2,000 for a king. Its table gives those numbers for the top thread only and says to double them if the bobbin uses the same thread.
Superior's table names sizes but doesn't give their dimensions. To turn it into a calculator, we assigned each size the common batting dimensions (crib 45 × 60, twin 72 × 90, queen 90 × 108, king 120 × 120 inches) and interpolated by area between them. That step is our assumption, not Superior's. A 60 × 72 quilt (4,320 square inches) falls between crib and twin, so at medium density it gets 400 + (4,320 − 2,700) ÷ (6,480 − 2,700) × 400 = 571 yards of top thread.
Straight-line quilting: line length
Parallel lines across a quilt add up to its area divided by the spacing: a 40 × 45 quilt quilted in lines 2 inches apart has 1,800 ÷ 2 = 900 inches of stitching one way, and 1,800 for a grid. That length goes through the same 2.5 × 1.15 lockstitch ratio, split half top and half bobbin.
The straight-line method gives much smaller numbers than Superior's averages for the same quilt. That's expected: free-motion paths curve and double back, and a meander covers far more distance than a ruler line across the same space.
How much to buy
Take the total, round up to whole spools, and if the total is close to a spool's capacity, buy one more. Running out of a thread color halfway through quilting and finding the new spool is a slightly different dye lot is a bigger problem than a spare spool in the drawer. A large cone or spool of 50 wt cotton, such as the 1,422-yard Aurifil 50 wt the form starts with, covers piecing for most quilts; change the yardage to match your spool.
Thread weight matters too. A thicker thread used for quilting (40 wt or 28 wt) puts fewer yards on a spool of the same size, so check the label rather than assuming.
Things that push the estimate up
- Tiny pieces: a 1-inch postage stamp quilt has three times the seams of a 3-inch one.
- Stitching in the ditch plus a fill: count both.
- Short stitch length. The Coats ratio assumes a standard stitch; denser stitches use more thread.
- Starting and stopping often, which leaves tails. The 15% waste allowance covers some of it.
- Ripping out and resewing a seam or a stretch of quilting.
Related pages
For choosing a quilting design and spacing your lines, see straight-line machine quilting and free-motion quilting for beginners. Your batting's package gives the widest spacing it allows; the batting guide explains why that matters. If someone else is doing the quilting, the longarm cost calculator prices it instead.
Products on this page
Photos and prices come from Amazon and can change.
Aurifil Mako Cotton Thread Solid 50WT 1422 YdsCheck price on Amazon
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