String that is used in blinds and shades is 100% polyester and is woven to withstand the rigors of blind operation. This type of string is NOT commonly sold in stores of any kind, so it must be either special ordered from a blind manufacturer, or ordered from Fix My Blinds.
There are many different diameter sizes of blind string and it is commonly measured in millimeters. String for cloth shades such as Cellular, Honeycomb and Pleated Shades, are usually .9MM or 1.2MM. String for Mini-Blinds is usually 1.4MM or 1.6MM. String for Wood, Faux Wood or Venetian Blinds can range from 1.6MM to 2.2MM. String for Roman, Woven Wood and Vertical Blinds can range from 1.8MM to 4.0MM. See table below:
To determine the diameter of string you need, follow the simple string wrap and measure technique in the video below:
What this technique does is effectively allow you to measure ten widths, or diameters, of the string, then convert it to inches and compare to the measurements on the Fix My Blinds website to determine the diameter of one width, or diameter. We provide the measurements for determining string diameter for blind string between .9MM and 4.0MM.