Threadsmith Pattern Block Drafter

Draft skirt, bodice, sleeve and trouser blocks from your measurements as tiled PDF, SVG or DXF.

Units of all lengths below

Blocks Straight skirt (front + back) Fitted bodice (front + back with darts) One-piece sleeve (cap fitted to the bodice armhole) Trousers (front + back)

The sleeve is fitted to the bodice armhole drafted from the same measurements.

More options

Body height

Standing, barefoot, from the floor to the top of the head. Empty = derived from the measurements you give.

Bust / chest girth

Horizontal girth over the fullest part of the bust (bust points) or chest, under the arms. Empty = derived from the measurements you give.

Waist girth

Horizontal girth at the natural waist, the narrowest part between the lowest rib and the hip bone. Empty = derived from the measurements you give.

Hip girth

Horizontal girth over the fullest part of the buttocks. Empty = derived from the measurements you give.

Neck base girth

Around the base of the neck through the nape (cervicale), the side neck points and the front neck point. Empty = derived from the measurements you give.

Back waist length

From the nape (cervicale) down the centre back to the waist line. Empty = derived from the measurements you give.

Front waist length

From the side neck point over the bust point straight down to the waist line. Empty = derived from the measurements you give.

Bust point depth

From the side neck point to the bust point. Empty = derived from the measurements you give.

Bust point separation

Horizontal distance between the two bust points. Empty = derived from the measurements you give.

Shoulder length

From the side neck point to the shoulder point (acromion). Empty = derived from the measurements you give.

Back width

Across the back between the armpit folds, about halfway between nape and underarm level. Empty = derived from the measurements you give.

Arm length

From the shoulder point over the slightly bent elbow to the wrist bone. Empty = derived from the measurements you give.

Upper arm girth

Horizontal girth of the upper arm at its fullest, just below the armpit. Empty = derived from the measurements you give.

Wrist girth

Around the wrist over the wrist bone. Empty = derived from the measurements you give.

Waist to hip

Vertical distance from the waist line to the hip line, at the side. Empty = derived from the measurements you give.

Body rise (crotch depth)

Seated on a hard flat chair: vertical distance from the waist line at the side down to the seat. Empty = derived from the measurements you give.

Waist to floor (outside leg)

At the side from the waist line down to the floor, barefoot. Empty = derived from the measurements you give.

Skirt length

Design measurement: from the waist at centre front down to the hem. Empty = derived from the measurements you give.

Ease (optional)

Wearing ease in the units above, as key=value. Keys: bodiceBust (bodice ease at the bust), bodiceWaist (bodice ease at the waist), skirtWaist (skirt ease at the waist), skirtHip (skirt ease at the hip), trousersWaist (trousers ease at the waist), trousersHip (trousers ease at the hip), crotch (ease in the body rise), upperArm (sleeve ease at the upper arm), wrist (sleeve ease at the wrist), capEase (sleeve cap ease).

Seam allowance

Empty = 1.5 cm or 5/8 in. Fold edges get none.

Hem allowance

Empty = 4 cm or 1 1/2 in.

Allowance corners

Hem corners

Sizes below yours

Sizes above yours

Girth step per size

Empty = 4 cm. Bust, waist and hip grow by this much per size; other measurements by a proportional rule.

Size in the files

Base, +1, +2 … or -1, -2 … of the size run.

Trouser hem circumference

Empty = 42 cm.

Paper for the tiled PDF

Page overlap

Empty = 1.5 cm.

File

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Try an example: Straight skirt from bust 92, waist 74, hip 100 cm (A4 tiles) · Bodice + sleeve with own ease, full-size SVG · Trousers in inches, graded one size up and down, DXF

More about this tool

How it works

Enter your body measurements (only bust, waist and hip are required — the rest is derived) and get sewing-pattern blocks drafted to them: a straight skirt, a fitted bodice with bust and waist darts, a one-piece sleeve whose cap is solved to the bodice armhole plus cap ease, and trousers. Each piece gets seam and hem allowance (mitred or squared corners, folded-hem corners), notches, grainline and darts trued to equal legs. The tool checks that the waist and hip of the drafted pieces equal your measurements plus ease, can grade a size run from your measurements, and writes a home-printable tiled PDF (A4 or Letter with overlap, crosses and a test square), a full-size SVG for plotters and projectors, or a DXF R12 file.

Measurements follow the landmark definitions of ISO 8559-1 (paraphrased). Missing measurements are derived from an own mid-range sample body: girths scale with your bust or hip, lengths with your height (or with the lengths you gave). No commercial size chart is used.
Blocks are an own geometric construction in the tradition of proportional drafting (Fales 1917, Vincent 1898, both public domain): skirt quarters with the side seam 5 mm towards the back; bodice back and front with back width, neck width neck/6 + 5 mm and armhole depth from the bust; a side bust dart whose intake makes the closed front side seam equal to the back; trousers with crotch extensions hip/16 (front) and hip/10 (back) and a 10° back seat angle.
Waist darts are solved numerically so the waist seam with darts closed equals waist + ease within 0.01 mm; darts are trued (shorter leg extended, dart cap on the closed seam line). The sleeve cap height is solved by bisection so the cap length equals the bodice armhole + cap ease.
Seam allowance: the seam line is flattened (0.05 mm tolerance) and every segment offset by its edge allowance (fold 0, hem, seam); convex corners mitred (squared off beyond 3× the allowance) or squared, concave corners trimmed, hem corners mirrored about the hem fold line, loops on tight inward curves removed.
Grading regenerates every size from measurements scaled by a grade rule (girths ± the step, neck/arm/lengths proportionally). Tiled print: printable area = paper − 10 mm margins, pages step by printable size − overlap, alignment crosses at the centre of each overlap strip, cover page with a 10 cm (or 4 in) test square and an assembly map.

A block is a starting point, not a finished garment pattern: make a test garment (toile) from cheap fabric and adjust the fit before cutting good fabric. Print at 100 % and measure the test square. Cloth simulation is not part of this tool.

Sources

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Draw or import artwork, turn it into stitches, export DST, PES, JEF or EXP files.

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Threadsmith Digitizer – Turn shapes, SVG paths, text or a whole project into embroidery stitches with stats and preview.

How to use the Threadsmith Pattern Block Drafter

Draft skirt, bodice, sleeve and trouser blocks from your own measurements, with seam allowance, grading and a tiled PDF you can print at home.

What it is for

A block (or sloper) is the plain, close-fitting base pattern every style is cut from. A commercial pattern means picking the nearest size from someone else's chart; this tool drafts the blocks to your body instead.

You need only three numbers — bust, waist and hip. Every other measurement (back length, shoulder, arm, body rise …) is derived from an own sample body scaled to what you entered, and you can overwrite any of them for a closer fit. The tool adds wearing ease, draws darts, notches and grainlines, adds seam and hem allowance and writes a tiled PDF for a home printer, a full-size SVG for a plotter or projector, or a DXF for CAD software.

It is not a style library and not a 3D fitting room. A block is a starting point that you test in cheap fabric (a toile) and adjust.

Worked example

The first example drafts a straight skirt for bust 92, waist 74 and hip 100 cm with a 60 cm skirt length. With the default ease (1 cm at the waist, 4 cm at the hip) the targets are 75 cm and 104 cm. The fit table shows exactly that: waist seam with darts closed 750 mm, hip line 1040 mm, and side seams of 615.08 mm on front and back. The A4 PDF has 13 pages: a cover page plus 3 rows × 4 columns of tiles.

For a custom run we entered bust 104, waist 88, hip 112, back waist length 42, waist to hip 21 and skirt length 65 cm, chose skirt + bodice, and graded one size down and two up. All 9 of 9 checks passed — bodice waist 920 mm (88 cm + 4 cm ease), underarm line 1140 mm (104 + 10), front side seam with the bust dart closed 201.68 mm, the same as the back. The PDF of the base size needs 25 pages, and a nest view shows the seam lines of sizes −1, Base, +1 and +2 on top of each other.

How to read the result

Fit checks compare what was drafted with what you asked for: waist (darts closed), hip or underarm line, side seams front = back, equal dart legs, and sleeve cap = armhole + cap ease. Every row should say yes; the tolerance is 1 mm.
Pieces lists each piece with its cutting instruction (Cut 1 on fold, Cut 2 (mirrored pairs)), size and area. The result also contains each cutting line as a polygon, ready for the marker tool.
Derived names the measurements filled in from the sample body; measure those yourself when the toile fits badly there.
The Open in Threadsmith link opens the same settings in the app's Pattern desk (marker, print, embroidery placement).

Tips and common mistakes

Print the PDF at 100 % / actual size, never "fit to page", and measure the test square on the cover page before you cut anything.
Measure snugly over light underwear; ease is added by the tool. Adding your own ease on top makes the block baggy.
A long body with a short waist? Enter back waist length and front waist length — the bust dart comes from their difference.
Ease values go into one text field, e.g. bodiceBust=8, capEase=1.2, in the same units as the measurements.
The sleeve is always fitted to the bodice armhole drafted from the same measurements, so change the bodice first.

FAQ

Where do the drafting rules come from?

They are an own geometric construction in the tradition of proportional drafting from public-domain manuals (Fales 1917, Vincent 1898); no commercial size chart or pattern is copied.

Can I use inches?

Yes. Choose inches and enter every length in inches; allowances default to 5/8 in and 1 1/2 in for the hem.

What does grading do?

It drafts every size again from your measurements plus a grade rule (bust, waist and hip ± the girth step per size), so darts and curves are correct in every size.

Why is my cap ease warning about the upper arm?

The sleeve cap must be at least as long as the sleeve is wide. Lower the upper arm ease or allow more cap ease.

Guide last updated: November 2, 2026

For scripts and AI agents

JSON API: POST https://threadsmithpatternblock.usefulweb.app/api/v1/calculate (same calculation as this page)
Interface description: OpenAPI 3.1 · AI guide: llms.txt
MCP server (Streamable HTTP): https://threadsmithpatternblock.usefulweb.app/mcp · tool name threadsmith_pattern_block

Example request

curl -s -X POST https://threadsmithpatternblock.usefulweb.app/api/v1/calculate \
  -H 'content-type: application/json' \
  -d '{"units":"cm","blocks":["skirt"],"bust":92,"waist":74,"hip":100,"skirtLength":60}'

Feedback · ideas & bug reports welcome