QuiltCutCalc · quiltcutcalc.com
Block & strip cutting plan
Top 70 × 90 in square: 100 target units; 5 in square 100 squares per color; 13 strips per color Buy 1.875 yd per color (1 colors) 100 units produced; 0 spare; 2 in squaring buffer per color
Finished top preset
44 − 1.5 in selvages − 2 in assumed width shrinkage/trimming = 40.5 in default net WOF. These deductions are editable planning examples; measure your own fabric after any washing. 108 in defaults to 104 in usable. A 4 in overhang is a starting point; ask your quilter. Net WOF is not deducted again.
Block & strip rotary cut yield
5 in starting square · 8 squares per WOF strip
13 strips × 5 in per color. 100 starting squares per color; produces 100 finished units (0 spare).
Buy 1 ⅞ yd (1.875) per color, 1 color. Includes 2 in squaring per color. Square cut size includes two ¼ in seams.
These conventional starting formulas include no extra trim-down allowance. Sew a test unit; for trim buffers or Magic 8, use the existing HST calculator. Strip yield is floor(usable WOF ÷ cut size); offcuts are not nested.
Selectable cutting notes
QuiltCutCalc block cutting plan square: 100 target units; 5 in starting square 100 squares per color; 13 strips per color Buy 1.875 yd per color (1 colors) 100 units produced; 0 spare; 2 in squaring buffer per color
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Rotary Block Subcut & Seam Allowance Reference Formulas
For the methods in this tool, add 0.5″ to a finished square or rectangle dimension for two ¼″ allowances, add 0.875″ (⅞″) to the finished size for the conventional two-at-a-time HST starting square, and use a 1.25″ (1¼″) starting-square addition for the four-triangle QST method. These are method-specific cutting rules; follow the pattern and allow extra if you plan to trim.
When designing custom quilt layouts or converting templates for rotary cutting, diagonal seam geometry differs from a straight square’s two edge allowances. The right-triangle relationship c = a × √2 helps explain the extra starting fabric, but it does not make a single 0.354″ corner deduction valid for every triangle method. USU Extension’s half-square triangle instructions support the conventional finished-plus-⅞″ two-square method; the other rules below are stated separately so that a method’s output is not confused with the number of starting squares.
- Standard squares and strips:
cut size = finished size + 0.5″. A 4″ finished square cuts at 4.5″, yielding 8 pieces across a 40″ usable WOF strip. - Half-square triangles, two at a time:
starting square = finished HST size + 0.875″. For a 4″ finished HST, start with 4.875″ squares. A pair of contrasting squares makes 2 assembled HST blocks. Adding 1″ instead of ⅞″ gives an extra ⅛″ for trimming; check the sewn unit before batch cutting. - Quarter-square / hourglass triangles: this tool uses
starting square = finished QST size + 1.25″, giving 5.25″ for a 4″ finished block. Cutting a square on both diagonals yields four triangles, not four finished hourglass blocks. A two-color pair supplies triangles for 2 assembled hourglass blocks. Verify the pattern’s grain direction, construction sequence and trim size. - Eight-at-a-time Magic HST method:
starting square = 2 × (finished HST size + 0.875″). A pair of those larger squares yields eight HST units, as shown in APQS’s Magic 8 formula. If you add a trimming buffer, apply it consistently before doubling and trim to the pattern’s unfinished size.
Need to calculate background fabric for 140 squares or plan sashing strips? Open Block & Strip Rotary Cutting Calculator → Run each fabric color and cutting size as its own batch. For a batch, pieces across a strip are rounded down, and required strip rows are rounded up; spare pieces do not cancel the need to buy a complete row.
Method References
Manufacturer and university guidance is linked for the specific techniques it supports. The calculations, sample prices, simulation and editable width assumptions are identified separately in the text.