Seam Allowance Calculator

Calculate the total extra fabric needed for seam allowances across all pattern pieces. Enter piece count, seam allowance width, and total seam length.

Inputs

Pattern Pieces

Seam Allowance

Total Seam Length

Tab to move between fields

Results

Extra Fabric (Total)

250 in

≈ 4 adult heights

Extra Fabric6.94 yd

Avg Seam per Piece25 in

Extra per Piece31.3 in

Seam Area250 sq in

Extra Fabric Feet$20.83

How to Use This Calculator

Enter the number of pattern pieces in the garment.
Set the seam allowance (inches) -- standard: 5/8 in US patterns, 1.5 cm European patterns.
Enter total seam length (inches) (sum of all seams in the garment).
Review extra fabric in inches and yards consumed by seam allowances and average seam per piece.
Add seam allowances to pattern pieces before cutting -- most commercial patterns include them, but fashion patterns may not.

How the result changes with Seam Allowance

Seam Allowance	Extra Fabric (Total)
0.38	150 in
0.69	275.2 in
1.06	424 in
1.38	552 in

What each input means

Pattern Pieces: Total number of pattern pieces in the garment
Seam Allowance: Width of seam allowance (common: 3/8", 1/2", 5/8")
Total Seam Length: Combined length of all seams in the garment

How this is calculated

Worked example, using the default values

Identify Input Parameters
Pattern Pieces = 8, Seam Allowance = 0.625, Total Seam Length = 200 = 3 input(s) provided
Calculate Extra Fabric
Extra Fabric
250 = 250
Calculate Extra Fabric
Extra Fabric
6.94 = 6.94
Calculate Avg Seam per Piece
Avg Seam per Piece
25 = 25

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