workroomtools. Language
The workroom toolkit
Work from a required strip length or a square of fabric you already have. Keep raw width, seam reserve, trimming and the one-strip tube offset visible in one practical planning record.
One supported method: a true square made into a parallelogram, then an offset tube with two joins. Output is an explicit planning estimate, not guaranteed production yield. Rectangular starts and individual joined strips use different geometry.
Example inputs: replace with your measured project.
Download example JSON · Private file processing in this browser. Export a backup for other devices.
CSV and PDF retain the estimate assumptions. Test the tube on a sample and measure the relaxed strip before relying on the yield.
Export JSON to keep a portable backup.
Raw strip width is the distance between cutting lines. It is not the visible finished binding width and not necessarily the number printed on a tape maker. Folding style, cloth thickness and how the binding wraps an edge affect that relationship. Prepare a short sample with your actual fabric and equipment, measure its unfolded width and enter that tested value.
Target mode finds a square whose estimated usable strip reaches the requested length under the selected reserves. Existing-square mode instead reports the estimated result of a measured square. Trim away selvages and square the cloth first. A rectangular remnant cannot be represented by averaging its sides: this version only supports a genuinely square start.
Enter the seam allowance for the two tube-method joins. Then choose an additional whole percentage for imperfect final bands, pressing and other trimming, and a total length to remove from the two strip ends. These are planning assumptions, not measurements of your sewing accuracy. Increasing a reserve should reduce yield or increase the required square; it should never be hidden inside an unexplained total.
The calculated square must fit within usable width. The page flags a square that is too wide and does not silently piece it from smaller scraps. You can obtain wider fabric or make separate batches with their own losses and later joins. Keep the JSON assumptions with the printed estimate, then record the relaxed strip length from a sample before preparing important work.
The square is divided diagonally, and its straight-grain edges are joined into a parallelogram. Mark parallel cutting lines at the selected raw width along the bias direction. The final incomplete band needs trimming; its existence is one reason that square area divided by width is an upper bound rather than a reliable production promise. The photograph illustrates the stage, not an exact geometry to trace.
The second seam forms a tube with the strip lines shifted by one band. The matching reference is where a line meets the sewing line, not simply where it touches the raw edge. Check the connection on a paper or scrap model: a correctly offset path leads from one end through the whole tube. A zero-offset arrangement produces separate rings instead of the intended continuous strip.
Check the numbers
The example uses target mode, a 2-inch raw strip, 180-inch target, quarter-inch tube seams, 10% extra trim reserve, 4 inches of end trimming and 44-inch usable fabric.
Bias cloth can lengthen when handled. Measure the strip relaxed after appropriate pressing, without pulling it along a ruler. Extra apparent length from stretching does not provide consistent width or stable finishing. The calculator records geometric planning lengths and does not model elastic recovery or fabric-specific distortion.
Single-fold tape, double-fold tape and quilt binding use different folding arrangements. Thick edges can consume additional width. This page accepts a confirmed raw width so it does not force a universal multiplier onto all those constructions. A width change can alter the feasible square and the number of visible bands.
Simply aligning chalk marks at raw edges can shift the cut path after the seam is sewn. Baste the proposed one-band offset and inspect the path on both sides before making the second permanent join. Work with a removable marking method suitable for the cloth and keep the opposite tube wall out of the cutting path.
The target should already include the length needed to join binding ends on the finished item and complete your chosen application. End trimming in this tool covers preparation of the newly made strip. Those are different operations. Record both decisions so a maker does not mistake a preparation estimate for an exact finished-project perimeter.
The method, explained
Rule version 1.0.0
For square side A, seam S and raw strip width W, gross area is A². The planning seam-area reserve is 4AS. Extra trim percentage T is applied to the remaining area, then the result is divided by W. Finally subtract total end trimming E. Estimated yield is max(0, (A² − 4AS) × (1 − T/100) / W − E), rounded downward at stored micrometer precision.
Target mode searches for the smallest side meeting the entered target under this model, then rounds upward to one-eighth inch or one millimeter. Both modes require a square at least four strip widths across and enough space for the selected seam reserve. These bounds keep tiny, impractical tube arrangements out of the estimate; they do not certify the final strip.
The seam-area budget and extra trimming percentage are explicit assumptions rather than an exact sewn-surface model. Incomplete bands, real seam geometry and operator technique change actual output. Compare a sample’s relaxed usable length with the estimate, adjust the reserve and keep that revised file. The drawing explains cutting order and offset; it is not a calibrated template.
Offset-tube construction background: Itch to Stitch continuous-loop tutorial
Choose target mode and enter the raw strip width, needed length and preparation reserves. The result is rounded upward to a practical square increment. It must still fit the usable cloth. Treat it as a planning estimate and confirm the selected losses with a same-fabric sample.
Choose existing-square mode and enter its trimmed side. The ledger shows the area-only ceiling, seam-area deduction, extra trim deduction and end trimming before the estimated usable length. This makes clear why the answer is lower than simply dividing square area by strip width.
The tube may have been joined without shifting the line connections by one strip. Check the diagram and test the seam with paper first. Matching adjacent lines at the sewing line creates a continuing path; matching each line straight back to itself closes individual rings.
This implementation supports a square start only. You may trim a usable square from a rectangular piece and enter that side, but the remaining fabric is not included in its yield. A full rectangular continuous-bias method needs a separate validated layout and should not be approximated by equivalent area here.
No. The formula budgets identifiable losses but cannot predict the exact incomplete band, pressing distortion or cutting accuracy. The printed record retains those assumptions. Make a sample, allow practical spare length and measure the finished raw strip without tension before relying on it.
Use the piping tool to establish the cord and covering-strip requirement first. This page helps prepare a continuous bias strip of a confirmed raw width. It does not calculate cord diameter, how much cloth wraps the cord or the installation allowance for a particular welt seam.
Review the measurements, keep a backup and print a proof.