Seam Allowance Total
Calculator
Results
- Allowance area per seam (cm²)
- 180
- Total seam allowance area (cm²)
- 1,440
- Total seam allowance area (m²)
- 0.144
- Total seam length (cm)
- 480
Craft results
| Allowance area per seam (cm²) | 180 |
| Total seam allowance area (cm²) | 1,440 |
| Total seam allowance area (m²) | 0.144 |
| Total seam length (cm) | 480 |
formula-map diagram
- Allowance area per seam (cm²)
- 180
- Total seam allowance area (cm²)
- 1,440
- Total seam allowance area (m²)
- 0.144
- Total seam length (cm)
- 480
Formula breakdown
Formula
A = 2 × sa × Ls × n= 180
Note
Simplified model: these are standard craft estimates based on rectangular layouts, quoted gauge and nominal densities. Real fabric nap, directional prints, shrinkage, pattern matching, yarn lots and supplier SAP values vary, so always make a swatch or test piece and buy a little extra.
More in Crafts and sewing
See all →Frequently asked questions
What exactly does 'seam allowance total' add up?+
It sums the seam allowance added on every edge of a pattern piece, so a piece with four seamed edges plus a hem adds each allowance separately, not just one flat amount. The total tells you the finished piece's cut size versus its sewn size.
Why isn't seam allowance the same on every edge?+
Different edges often need different allowances: garment seams commonly use 1/4in to 5/8in, while hems and waistbands need 1in or more to fold under. Enter each edge's allowance separately rather than assuming one uniform value.
How does this affect the finished garment size?+
Seam allowance is consumed by the seam itself and does not add to the finished measurement, it only affects how big you cut the fabric piece. Miscalculating it is a common reason a finished garment comes out smaller or larger than expected.
Do curved seams need a different allowance than straight ones?+
The allowance width can stay the same, but curved seams (armholes, necklines) are harder to sew accurately at a wide allowance and are often clipped or notched after sewing. A narrower allowance, around 1/4in to 3/8in, is easier to control on tight curves.
Why would I calculate this instead of just trusting the pattern?+
Commercial patterns already include seam allowance, but many indie, vintage, or self-drafted patterns give only the finished size and expect you to add your own. This calculator prevents cutting pieces too small when you're adding allowance yourself.