Pattern Resize Calculator: percentage scaling and sewing grades
Key takeaways
- Knitting: original vs desired dimensions → scale % per part, stitch counts and row counts at your gauge, rounded to whole numbers.
- The calculator flags stitch counts that break ribbing repeats (1×1 needs even, 2×2 needs multiples of 4).
- Sewing: pick two sizes from a published standard chart (Simplicity Misses) → per-measurement grade differences.
- Percentage scaling is exact for rectangles and misleading for shaped areas — armholes and necklines do not scale with circumference.
- All math runs locally in your browser.
Knitting: percentage resize with stitch counts
Enter the pattern's original width and length per part, and the dimensions you want. Leave a "desired" box blank to keep that dimension unchanged. The percentage helper fills every desired box at once (e.g. 110 = +10%).
| Part | Orig. width (cm) | Desired width (cm) | Orig. length (cm) | Desired length (cm) |
|---|---|---|---|---|
How the knitting resize works — and where it stops working
The arithmetic is transparent: scale % = desired ÷ original × 100, and stitches = width (cm) × stitch gauge ÷ 10, rounded to the nearest whole stitch (0.5 rounds up). Rows work the same way with row gauge. That much is exact — it is the same formula from knitting math explained, run in both directions.
The ribbing note exists because repeats are rigid: 1×1 ribbing needs an even count, 2×2 needs a multiple of 4, and cables chart their own repeat. A scaled count of 103 for a 2×2 brim is unusable as-is; the calculator points you to the nearest workable count (100 or 104) so you can decide whether to give up a centimetre or gain one.
Limits of the percentage method
Uniform scaling assumes the whole object stretches equally. Real garments do not: armhole depth, neck width and shoulder slope change far less between sizes than chest circumference does, and adults rarely want length scaled by the same factor as width. For fitted garments, the professional route is grading between pattern sizes — the sewing logic below — or finding the pattern at the right size. The full discussion is in Adjusting a knitting pattern larger or smaller.
Worked example (the preloaded row). A child's hat written at 48 cm × 20 cm, resized to 54 cm × 22 cm at gauge 20 sts & 28 rows per 10 cm: width scales to 112.5%, length to 110%; stitches go 96 → 108 (108 divides by 4 — the 2×2 brim survives), rows 56 → 62. A target of 51 cm instead would give 102 stitches — flagged as not divisible by 4, nearest workable counts 100 or 104.
Sewing: grade differences from a published size table
Pick a "from" and a "to" size from the embedded chart — Simplicity's official Misses' body measurements — and the calculator lists the raw grade difference per measurement, plus a naive per-side-seam split as a sanity check.
Your own measurements (any unit, keep it consistent)
| Measurement | Base | Target |
|---|---|---|
How grading works
Grading answers: "the pattern is a 12, my body measures like a 16 — where exactly does the extra fabric go?" The raw differences are the easy part: size 12 → 16 in the Simplicity chart is +4" bust, +3½" waist, +4" hip, +½" back-waist length. The craft is distribution: professional grade rules walk the pattern outline and add fractions at side seams, darts, armhole and neck so proportions stay human. Those rule tables live in patternmaking references — the standard texts are Winifred Aldrich's Metric Pattern Cutting and the major pattern-drafting manuals; we cite them rather than reproduce their tables. The method-level walkthrough is in Sewing grade rules, explained simply.
Worked example. Grading a bodice from your base 90 cm bust to a 96 cm target with 4 grading points (two side seams, two bust darts): +6 cm total, +1.5 cm per point — half on each side seam at the bust level, the rest swallowed by the darts. The calculator's per-point column does exactly this split for any measurement.
FAQ
Can I resize any knitting pattern by percentage?
Rectangular and tube projects, yes: scarves, wraps, blankets, simple hats, drop-shoulder pullovers. Fitted garments with shaped armholes and sleeves need size-graded thinking instead — or a pattern already written for your target size.
Do I scale stitch counts or just recalculate from dimensions?
Recalculating from dimensions at your gauge (what this tool does) is more reliable than multiplying the pattern's counts, because your gauge almost never matches the pattern's exactly.
Why is back-waist length graded so much less than bust?
Because humans grow wider faster than taller. Published charts reflect measured populations — in the Simplicity chart bust gains 1–2" per size while back-waist length gains about ¼". That asymmetry is exactly why blanket percentage scaling distorts garments.
What's the difference between grading and just adding seam allowance?
Seam allowance is a fixed construction margin, identical on every size. Grading changes the fitted dimensions themselves. One is 1.5 cm everywhere; the other is a proportional, point-by-point edit.
Clear gridded ruler & French curve set
Walking pattern edges by grade increments is dramatically easier with a see-through gridded ruler — the standard grading toolkit starter.
Check price →Related reading
- Adjusting a knitting pattern larger or smaller — the method and its limits, in full
- Sewing grade rules, explained simply — distribution logic and the references to trust
- Standard body measurement tables — CYC knitting sizing plus head circumferences