Thread Consumption Calculator
Thread is several times the seam length.
Calculate thread consumption from seam length and stitch type, with wastage and the number of cones a production run needs.
Thread needed
28.7 m
2.5× the seam length, plus 15% wastage
Overlocking uses far more thread than assembly because the threads loop around the fabric edge rather than passing straight through. Shorter stitches use more thread over the same distance, so tighten these ratios for topstitching and dense work.
How the Thread Consumption Calculator works
Thread travels through the fabric rather than along it, so a seam consumes several times its own length in thread — and how many times depends entirely on the stitch. A lockstitch uses about two and a half times; a four-thread overlock around eighteen. That difference is why overlocking a garment costs more thread than assembling it.
Also known as: thread usage calculator · thread requirement calculator
Why thread is a multiple, not a length
Thread does not run along a seam, it runs through it — up and down through the fabric with every stitch. So a seam consumes several times its own length in thread, and the multiple depends entirely on the stitch structure.
A lockstitch, with two threads interlocking in the middle of the fabric, uses about 2.5 times the seam length. A four-thread overlock, where the threads loop around the raw edge, uses around 18 — because four threads each travel a much longer path per stitch.
That is why finishing a garment can use more thread than assembling it, and why an overlocker empties cones at a rate that surprises people coming from a domestic machine.
A worked example
Ten metres of seam sewn as lockstitch uses about 25 metres of thread, or 28.75 with a 15% wastage allowance for tails, re-threading and breakages.
The same ten metres overlocked with four threads uses 180 metres before wastage — over six times as much. A production run of a hundred garments at ten metres each needs three 1,000 metre cones for the overlocking alone.
Where the answer misleads
Stitch length changes consumption directly: shorter stitches mean more of them over the same distance, so more thread. The standard ratios assume a typical stitch length, and topstitching or dense decorative work uses considerably more.
Fabric thickness matters too, since the thread has to travel through it. The same stitch on heavy canvas uses more thread than on lawn, and the published ratios are averages across typical weights.
Finally, the ratios are for a single line of stitching. A seam that is sewn, overlocked and topstitched has consumed three separate allocations, and estimating a garment means adding up every operation rather than measuring the seam once.
Frequently asked questions
How much thread does a seam use?
Around 2.5 times the seam length for a lockstitch, 4 for a chainstitch, 14 for a three-thread overlock and 18 for a four-thread. Coverstitch is higher still at about 20.
Why does overlocking use so much more?
Because the threads loop around the fabric edge rather than passing straight through. Each of the three or four threads travels a longer path per stitch, and they are counted together.
How much wastage should I allow?
Ten to twenty percent covers thread ends, re-threading, breakages and the tails at the start and end of each seam. Production estimates typically use fifteen percent.
Does stitch length change consumption?
Yes — shorter stitches use more thread over the same distance, because there are more of them. The ratios here assume a typical stitch length, so tighten them for topstitching and dense work.