Planner · Sewing & craft
Scale a pattern from its measurements to yours — without guessing
Enter the measurements printed on your pattern and your own body measurements, then see the exact scale ratio, how much to add or trim at each seam, and a grading step for every 5 cm. All maths stays in your browser.
Settings
units & garmentMeasurements
original → target| Measurement | Original | Target (you) | Seams |
|---|
Bust, waist and hip are circumferences. Lengths are single-piece. Seams is how many seam lines share the difference (2 for side seams, 1 for centre back, etc.).
How to use
- Choose cm or inch.
- Pick a preset or type the pattern's printed sizes into “Original”.
- Type your body (or desired finished) sizes into “Target”.
- Set how many seams share each circumference.
Original vs target
silhouette + ratio barsPer-measurement scale
Bars show target ÷ original. Centre is 1.00 — left means take in, right means let out.
Scale & seam table
per measurement| Measurement | Original | Target | Ratio | Difference | Per seam | Note |
|---|
Grading table
5 cm / 2 in steps| Size step | Bust | Waist | Hip | Per-seam (bust) |
|---|
Each step is 5 cm in cm mode or 2 in in inch mode — the increments most publishers use between sizes. Use the row whose bust is closest to your target, then tweak per row.
Printable alteration checklist
tick as you cutWhat to do next
How the numbers are worked out
Every figure below is arithmetic you can check by hand. Nothing is fetched from a server.
Ratio & difference
For each row: ratio = target ÷ original and
difference = target − original. Both are shown in the unit
you chose. Median ratio is the middle of all ratios; spread is
max − min.
Per-seam adjustment
A circumference is split across seams:
per-seam = difference ÷ pieces and
per-edge = per-seam ÷ 2 when you cut on the fold. Positive
means let out, negative means take in, measured on the pattern piece.
Seam allowance
If “includes SA” is ticked, finished sizes are
finished = measured − 2 × SA on each side first.
Comparison uses finished sizes, but the reported add/trim is back in
on-pattern terms so you know where to draw.
Grading step
Size steps are 5 cm (or 2 in). The table adds
k × step to the original bust/waist/hip and shows
per-seam = k × step ÷ pieces for that row. Pick the row
nearest your target. Preset values are typical body measurements, not
one publisher's chart.
What this is not: proportional scaling only; it does not reshape armholes, necklines or darts, and any scale beyond about 15 % usually needs a real pattern alteration.
Questions
Do I enter the pattern's finished garment or the body measurements?
Enter the measurements printed on the pattern envelope or the tissue itself. If the pattern includes seam allowance, tick that box and the tool first converts to finished dimensions before it compares, so you do not double-count the allowance.
When should I alter instead of scaling the whole pattern?
When the spread between your bust, waist and hip ratios is more than about 10 %, or any single measurement needs more than a 15 % change, scale alone will distort armholes and darts. Grade between sizes or slash-and-spread the piece instead.
What does per-seam adjustment mean?
A circumference is shared across several seams. For example a 4 cm hip difference split across two side seams means 2 cm per seam, or 1 cm per pattern edge if you cut on the fold. The table shows the exact add or trim at each seam line.
Is the grading table the same as the pattern's size chart?
No. The grading table here is a planning estimate using 5 cm (about 2 in) steps from your pattern size. Always check the publisher's own size chart for the canonical body measurements.
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