Thread consumption is the length of sewing thread used to make one garment. It is needed to order thread by color and ticket, and to cost thread in the bill of materials. The most practical method is the ratio method: measure how much thread each stitch type uses per centimeter of seam, then multiply by the seam lengths in the garment.
The formula#
- Seam length: length of each seam in cm, grouped by stitch type.
- Ratio: cm of thread used per cm of seam for that stitch type, including all threads (needle, bobbin, loopers, cover threads).
- Wastage: allowance for thread chains, trimming, re-threading and breakage.
Measuring a ratio#
The ratio depends on stitch type, stitch density, fabric thickness, seam width and thread tension. Measure it on the production fabric at the production settings:
- Sew a known length of seam, for example 10 cm.
- Unpick all threads of the stitch carefully.
- Straighten each thread without stretching it and measure its length.
- Ratio = total thread length / seam length.
For stitches with several threads, measure each one: needle threads and looper threads are often ordered in different types (for example spun polyester needle thread and textured looper thread).
Indicative ratios#
These values only show the order of magnitude. Measure your own.
| Stitch type | Approximate thread per cm of seam |
|---|---|
| 301 lockstitch | 2.5 |
| 401 two-thread chainstitch | 5.5 |
| 504 three-thread overlock | 14 |
| 514 four-thread overlock | 18 |
| 406 two-needle coverstitch | 16 to 18 |
| 516 safety stitch | 20 |
Worked example: T-shirt#
| Seam | Stitch | Length (cm) | Ratio | Thread (cm) |
|---|---|---|---|---|
| Shoulders and side seams | 514 | 150 | 18 | 2,700 |
| Sleeve attach | 514 | 100 | 18 | 1,800 |
| Hems | 406 | 190 | 16 | 3,040 |
| Neck topstitch | 406 | 50 | 16 | 800 |
| Label | 301 | 10 | 2.5 | 25 |
| Total | 8,365 |
Net thread = 8,365 cm = 83.65 m. With 12% wastage: 83.65 × 1.12 = 93.7 m per garment.
For an order of 5,000 pieces with 4,000 m cones: 93.7 × 5,000 / 4,000 = 117.1, so 118 cones, split by thread type and color.
Splitting by thread type#
Most knit seams use two thread types:
- Needle threads: spun polyester.
- Looper and cover threads: textured polyester.
Measure each thread's share of the ratio, and calculate consumption and cones separately for each type and color.
Common mistakes#
- Using ratios from a table instead of measuring on the actual fabric and SPI.
- Forgetting small seams such as bartacks, buttonholes and labels.
- One cone count for all colors when the order has several colors with different quantities.
- Ignoring minimum cones per machine: each machine needs a full set of cones in each color, even for a short run.
Use the thread consumption calculator to run the numbers.
Related guides#
- Stitch types: the stitch classes behind the ratios in this method.
- Sewing thread selection: choosing thread type and ticket for each seam.
- Stitch density (SPI): why stitch density changes the thread ratio.
- Bill of materials: listing threads by color and type in the bill of materials.
- Garment costing: where thread cost appears in the garment price.
- Thread breakage: thread problems that increase wastage on the line.
Frequently asked questions#
How accurate is the ratio method? Accurate enough for ordering when ratios are measured on the production fabric at the production SPI. Using generic ratios can give errors of 20% or more.
Why is overlock thread consumption so high? Overlock stitches wrap around the fabric edge with several threads, so each centimeter of seam uses many centimeters of thread.
Should I order a safety margin? The wastage percentage is the margin. Add more only for known risks, such as a new operator group or frequent style changes.