Guide
Density is how tightly stitches are packed. Get it wrong and the design either shows the fabric through it or turns into a stiff, puckered patch. This page explains density, the push-pull distortion that makes shapes sew narrower than you drew them, and the pull compensation that corrects it.
Density is the spacing between adjacent rows in a fill or between adjacent stitches in a satin column, usually quoted in millimetres. Smaller spacing means more stitches, more coverage, more thread, and more stress on the fabric. A standard fill sits around 0.4 mm row spacing; open or light coverage goes wider.
Denser is not better. Excess density is the single most common cause of puckering, thread breaks, and needle deflection. It also drives up stitch count, run time, and thread cost. The goal is the lowest density that fully covers the fabric.
As the needle sews, thread tension pulls the fabric inward along the stitch direction and pushes it outward at the ends. A satin column drawn 6 mm wide can sew at 5.5 mm, leaving a gap against the neighbouring colour. The effect grows with column width, density, and fabric stretch.
Pull compensation fixes it by widening the shape slightly perpendicular to the stitch direction so the sewn result lands at the intended size. Stichii exposes pull compensation per object and applies a fabric-appropriate default from the preset — knits and spandex get the most, leather and stable wovens get almost none.
Puckering is fabric distortion, and it comes from three places: too much density, too little stabiliser, and poor hooping. Density is the one under your control in the design file. If a test sew-out puckers, reduce density before you reach for heavier stabiliser.
Stichii estimates stitch count, thread consumption, and sew time from the actual stitch stream, so you can see the cost of a density change before you sew it rather than after.
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