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Monday, February 17, 2014

It's SEW Mathematical! - Using Area & Width to Find Length

What do you do when your fabric dimensions are different from those required by a pattern?  How do you determine the amount of fabric you will need for your project?  

Recently I considered making a vintage dress pattern.  The suggested pattern requirements were based on fabric that was 36” wide but the fabric that I wanted to use was 60” wide.  Surely I would need less fabric since my fabric was wider...but how much fabric would I need?  

Since fabric, uncut, in it's "single thickness" state, resembles a quadrilateral - a four-sided, two dimensional shape with four corners, - I used the "Area of a Rectangle" Formula and the information given in the pattern, to determine the area of fabric that I would need for the project.  Once the area is calculated, it can then be divided by any width to find the length.  
First, I converted yards to inches so that I would be working with one unit of measure, in this case inches.   To convert yards to inches, multiply the number of yards by 36 – since there are 36 inches in each yard.

2 1/2 yards x 36 inches per yard = 90 inches

Once I converted the length to 90 inches, I multiplied it by the width of 36, to get an area of 3,240 square inches.  Based on the fabric dimensions given in pattern, I would need 3,240 square inches of fabric to complete the project.  

Please note, rectangle is a "sketch" and not drawn to scale.

Next, I divided the area (3,240 square inches) by 60 (which was the width of my fabric) - to determine the length of fabric that I would need for the project: 

3,240 square inches         =       54 inches long
              60 inches wide

Since we usually associate fabric length with yards, I converted 54 inches to 1 ½ yards by dividing 54 by 36. To convert inches to yards, divide the number of inches by 36 – since there are 36 inches in each yard.  Therefore, using this method, I calculated that I would need 1 ½ yards of 60" wide fabric to complete the project.  Then it becomes a matter of pattern (pieces) placement to get the most efficient layout.  Make sense?  

This is one way you can avoid purchasing (or cutting when it's from your own stash) too much or too little fabric when your fabric dimensions differ from those stated in a pattern.  Hope this helps! 

 Until next time....PEACE AND BLESSINGS!


1 comment:

  1. You still have to use common sence and not only matematics. I could make a rectangle 1 inch by 3240 inches. The area would still be 3240 square inches, but you are left with a useless and very long piece of fabric.
    I find it more usefull to lay out the pattern pieces to determine how much to buy.

    And on another note: I am gla we use centimeters, that saves us the hassle of converting.


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