Weaving Sett Calculator
Last updated: April 16, 2026
Find the right sett (EPI) for your yarn and weave structure, plus warp length and reed substitution.
Why You Need a Weaving Sett Calculator
Wrong sett in weaving creates fabric that is either sleazy — so open that warp threads shift and gaps appear — or stiff as a board because the threads are packed too tightly to interlace with any drape. Getting your ends per inch right before warping is the single most important decision in any weaving project.
Sett depends on yarn thickness, weave structure, and intended fabric hand. A yarn that works beautifully in plain weave at 10 ends per inch might need 12 or 14 for twill. Calculating sett from your measured wraps per inch removes the guesswork and prevents the heartbreak of cutting a failed project off the loom.
What Is a Weaving Sett Calculator?
A weaving sett calculator determines the ideal ends per inch (EPI) for your warp based on your yarn’s wraps per inch (WPI) and your chosen weave structure. Sett is the spacing of warp threads across the width of the loom — it controls how densely the threads pack and directly determines the fabric’s weight, drape, and durability.
Different weave structures require different sett densities because of how warp and weft interact. Plain weave, where every thread alternates over-under, needs the most open sett. Twill, where threads float over two or more before interlacing, allows a denser sett. Satin, with even longer floats, can be set denser still.
The calculator also computes total warp ends and warp length. Multiply EPI by the weaving width to get total ends, then add loom waste and shrinkage allowance to the desired finished length to get the total warp length you need to measure and wind.
How Weaving Sett Is Calculated
Start by measuring your yarn’s wraps per inch: wrap the yarn around a ruler for one inch with wraps touching but not overlapping. If you count 16 wraps in one inch, your yarn is 16 WPI. This measurement is the foundation of all sett calculations.
Plain weave uses approximately 50 percent of the WPI as the sett. So 16 WPI times 0.5 equals 8 EPI. Twill uses about 60 percent: 16 times 0.6 equals 9.6, which you round to 10 EPI. Satin uses about 70 percent. These percentages account for the space each weft pick needs to interlace between the warp threads.
To find total warp ends, multiply the sett by the weaving width. For a 20-inch-wide scarf at 10 EPI, you need 200 warp ends. Add 2 floating selvedge threads (one on each side) for a total of 202 ends to wind. Then multiply the desired length plus loom waste (typically 18 to 24 inches) for total warp yardage.
A calculator that determines the correct sett (ends per inch) for your yarn and weave structure, with warp length, loom waste, and reed substitution.
Weavers planning a new project who need to calculate how many warp ends to wind and which reed dent to use.
Enter your yarn WPI and weave structure to get the recommended sett, total warp ends, and warp yardage.
Weaving Sett Calculator Tool
How to Calculate Sett and EPI
Weaving Sett Results and Reed Substitution
Recommended Sett
4–5 EPI
Target: 5 ends per inch for Plain Weave (Tabby)
Based on ~9 WPI. Always sample first — fiber, twist, and finishing change sett.
4–5 EPI
Sett Reference by Structure
| Structure | Factor | Description |
|---|---|---|
| Plain Weave (Tabby) | 50% of WPI | Over one, under one. Firmest structure. |
| Twill (2/2) | 60% of WPI | Diagonal pattern. Denser than plain weave. |
| Twill (3/1) | 65% of WPI | Warp-dominant twill. Very dense. |
| Basket Weave | 50% of WPI | Pairs of threads over and under. |
| Satin (5-shaft) | 70% of WPI | Long floats. Drapey, dense sett. |
| Lace Weave | 35% of WPI | Open structure. Lower sett for holes. |
| Waffle | 55% of WPI | Textured, thick. Medium-high sett. |
How to Use the Weaving Sett Calculator
Enter your yarn's wraps per inch (WPI) — the number of times the yarn wraps side by side in one inch without overlapping or leaving gaps. Select your weave structure: plain weave, twill, satin, or lace. The calculator returns the recommended sett in ends per inch (EPI) and can also calculate total warp ends and warp length based on your project dimensions.
The relationship between WPI and sett depends on the weave structure. Plain weave typically sets at half the WPI. Twill sets denser because the float structure allows threads to pack more closely. Lace weave sets more openly to allow the pattern gaps to show.
Understanding Your Results
EPI (ends per inch) is the number of warp threads per inch across the width. PPI (picks per inch) is the number of weft passes per inch along the length. For a balanced weave — where warp and weft are equally visible — EPI and PPI should be roughly equal. If your EPI is higher than PPI, the warp dominates and you get a warp-faced fabric. Lower EPI relative to PPI creates a weft-faced fabric.
Sett affects both the drape and structure of your finished cloth. A tighter sett (more EPI) produces a firmer, stiffer fabric suitable for bags, upholstery, and rugs. A looser sett creates drapey fabric for scarves and garments. The calculator's recommendation is a starting point — always weave a sample to confirm the hand of the fabric.
Pro Tips
From 30+ years of fiber arts experience
- ✓Measure WPI by wrapping your yarn around a ruler for one inch. Do not overlap wraps or leave visible gaps between them. The wraps should sit side by side, just touching.
- ✓Wool shrinks 10-20% in wet finishing. Add that percentage to both your warp length and weft calculations. Cotton shrinks 3-5%. Linen shrinks minimally.
- ✓For rigid heddle weaving, your sett is fixed by the heddle you own (typically 8, 10, or 12 dent). Check that your yarn's recommended sett is compatible with your heddle before warping.
- ✓Tie on 6-8 extra warp inches beyond your project length for loom waste. The yarn between the breast beam and back beam cannot be woven.
What This Technique Does to Your Fabric
Weaving sett directly controls fabric hand and durability. Correct sett creates cloth that is neither sleazy (threads shift and gaps appear) nor stiff (threads pack so tightly the fabric loses drape). The visual effect is profound: too-loose sett produces open fabric where warp and weft are clearly visible as separate systems; correct sett balances the two so they appear visually integrated; too-tight sett produces dense, stiff fabric suitable only for rugs or upholstery. Sett also affects shrinkage percentage and wet-finish behavior — tightly set fabric shrinks less (threads are already compressed and have less room to move), while loosely set fabric shrinks more. The technique determines whether your finished cloth drapes beautifully or stands away from the body stiffly.
Step by Step
- 1Wrap the target yarn around a ruler for one inch, keeping wraps touching but not overlapping, and count the wraps per inch (WPI).
- 2Select your weave structure (plain weave, twill, satin, or lace) based on your project.
- 3Apply the structure-specific multiplier: plain weave = 50% of WPI, twill = 60% of WPI, satin = 70% of WPI, lace = 40% of WPI.
- 4Round the result to the nearest whole number for your ends per inch (EPI) sett recommendation.
Fiber-Specific Notes
Different fibers behave dramatically differently at various setts. Wool accepts both tight and loose setts gracefully, producing beautiful cloth across a range. Cotton needs slightly tighter sett than wool for the same yarn weight — the lack of elasticity means loose sett produces obviously gappy fabric. Linen accepts very dense sett beautifully without becoming stiff because of its natural smoothness; linen cloth can be tightly set and still drape. Alpaca and mohair require careful consideration of sett — tight sett can compress the loft out of these fibers, while loose sett makes them appear fuzzy and uncontrolled. Blended fibers (wool/silk, cotton/linen) sett according to the dominant fiber's characteristics.
Practice Project
On a rigid heddle loom (which has fixed sett teeth), measure the WPI of a worsted weight yarn, calculate what sett you would need for plain weave, and identify which heddle dent (8, 10, or 12) is closest. Warp the loom and weave a 12-inch sampler, noting how the fabric hand and appearance compares to your expectations based on the sett calculation.
References and Industry Standards
- Craft Yarn Council — Yarn Weight System — Industry-standard yarn weight categories and gauge ranges
- Craft Yarn Council — Needle & Hook Sizes — Standard sizing charts for knitting needles and crochet hooks
- Ravelry — Yarn database, pattern library, and community for fiber artists
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Frequently Asked Questions
What is sett in weaving?
Sett (also called EPI — Ends Per Inch) is the number of warp threads per inch in your fabric. The right sett depends on your yarn weight and weave structure. Too open = sleazy fabric. Too tight = stiff and warp-dominant.
How do I calculate sett?
The standard method: wrap your yarn around a ruler for 1 inch, count the wraps (WPI), then multiply by a factor based on your weave structure. Plain weave uses 50% of WPI, twill uses 60%. Our calculator does this automatically.
What is loom waste?
Loom waste is the unusable warp length tied to the loom. It includes the warp tied to front and back beams plus any unusable length. Typical loom waste is 18–36 inches depending on your loom.
How do I substitute a different reed?
Use our Reed Substitution tab. Enter your desired EPI and your available reed dent, and we’ll tell you how to thread it (e.g., alternate 1 and 2 threads per dent).
How much yarn do I need for weaving?
Enter your project dimensions, sett, and loom waste in our Warp Length tab. We calculate total warp and weft yardage including shrinkage allowance for your fiber type.
Does fiber type affect sett?
Yes. Sticky fibers like wool can be sett closer because they grip each other. Slippery fibers like silk or bamboo need a tighter sett (more threads) to prevent shifting.
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