Fabric width limits, and cutting a circle skirt from narrow fabric

You can always buy more length. You cannot buy more width once the fabric is cut, and for a circle skirt the width is usually what stops you.

Width sets a hard ceiling on length

A circle skirt panel is a piece of a ring. Whatever fraction of the circle it is, it has to fit across the fabric. Rearranged, the geometry gives you a ceiling:

maximum finished length = (usable width ÷ pieces across) − waist radius − hem allowance

Work an example. Fabric 45 inches wide, half an inch trimmed from each selvedge, so 44 inches usable. A 28 inch waist, cutting a full circle in four panels, one radius across:

waist radius = 28 ÷ 6.28 ≈ 4.5 inches
hem allowance = 1 inch
maximum length = 44 − 4.5 − 1 = 38.5 inches

Comfortable. Now try the same fabric with a full circle cut in one piece, which needs the whole diameter across the width — effectively 22 inches of radius:

maximum length = 22 − 4.5 − 1 = 16.5 inches

Same fabric, same waist, same skirt. The construction alone moved the ceiling by 22 inches.

Usable width is not the width on the label

Three things eat into it before you cut anything:

Selvedges. The woven edges are denser, often distorted, and sometimes printed with the manufacturer’s name. Most people trim between a quarter and three-quarters of an inch from each side.
Rounding on the bolt. A “45 inch” fabric is frequently 44, and a “60 inch” is often 58. Measure it.
Shrinkage. If you prewash — and for a skirt you should — expect a natural fibre to lose two to five per cent across the width. Prewash first, measure second.

Plan against what your tape measure says, not what the bolt end says.

When width is the problem, panels are the answer

Splitting the skirt into more pieces reduces what each piece needs across the width, roughly in proportion:

One piece needs the full diameter.
Two halves still need the full diameter, but each takes less length.
Four quarters need only one radius.
Six or eight panels need less again, though the pieces start to nest awkwardly and the saving tails off.

The cost is seams. Four panels means four vertical seams in a flared skirt, which on a plain fabric is invisible and on a bold print can be very visible indeed. It also means matching, if there is anything to match.

Narrow fabric is not a failure

If a full circle will not fit, the honest answer is usually one of these, and none of them is a compromise on quality:

Go shorter. Two inches off the length often converts an impossible layout into a comfortable one.
Go less full. A three-quarter circle keeps almost all of the movement for noticeably less fabric. A half circle still reads unmistakably as a flared skirt.
Add panels. More seams, more fabric-efficient, no change to the finished silhouette.
Change fabric. Quilting cotton is usually 44 inches; dress fabrics and linens are often 58 to 60. The wider bolt may cost less overall because it wastes less.

The circle skirt calculator evaluates all of these against your actual measurements at once, so you can see which trade you would rather make instead of guessing at one and re-checking by hand.