Sewing geometry · One full-circle panel
Mark the cut arcs with the allowances in the right direction.
Start with a chosen stitched opening and finished radial length. Find the inner cut radius, outer cut radius and enclosing square for one flat, unbroken full-circle panel.
Free · Centimetres · Browser-localYour chosen dimensions
This is a geometric panel draft, not a garment fit calculator. Choose an opening that suits your own construction, ease and hip clearance. No closure, waistband or joining seams are designed here.
Your approximate draft
Inner waist cut radius, from the common centre
cm
- Stitched opening radius
- cm
- Finished hem radius
- cm
- Outer hem cut radius
- cm
- Minimum unfolded square side
- cm
Solid blue: cut edges. Inner dashed orange: stitched opening. Outer dashed purple: finished hem. The enclosing square is the flat blank.
- Finished hem circumference
- cm
- Flat cut-panel area
- cm²
- Cut radial thickness
- cm
All output geometry is approximate. Display uses up to 12 significant digits, with nonzero small values retained. Extra digits are mathematical detail, not physical marking accuracy. Exported raw numerical values do not use display rounding.
The square is a single-piece geometric envelope, not yardage to buy. This diagram is not a print-to-scale pattern. Fabric growth, shrinkage, grain, pattern matching, defects and cutting margins are not included.
The waist allowance goes inward
The stitched opening is larger than its cut edge. Subtract the allowance from the opening radius, rather than adding it to the circumference.
The hem allowance goes outward
The finished length is measured from the stitched opening line. Add the hem allowance outside the intended finished hem without shortening that length.
One panel, one model
This draft is a full circular ring from a flat square. Partial circles, radial seams, zips, slits and waistband pieces need a different construction plan.