1. Grab your cord, a Pencil and Ruler
2. Wrap the cord around that pencil 10 times tightly
3. Squeeze the cord together
4. Grab that ruler and measure width of the cord
5. Divide the width by 10 and will by the Diameter of your cord​

Eg: If the 10 loops measures 14mm. 14 Divide by 10 =1.4mm 
The diameter is 1.4mm

Blind Repair has a couple of different thickness of string that you can use to restring your blinds and shades. A question that often gets asks is “What is the difference between string and cord?” To answer this questions, let’s look at a the definitions of the terms we are working with.
Cord is defined as a long, thin flexible string or rope made from several twisted strands. String is defined as material consisting of threads of cotton, hemp, or other material twisted together to form a thin length. Semantically speaking, “string” has an inferred meaning of something thinner and smaller, while “cord” often refers to something thicker and more substantial. Here at Blind repair, we’ve also heard this material referred to as rope, thread, line and twine. But, looking at the definitions of those words shows that they are made up of a length of material that is created when braiding or twisting strands together, just like string and cord.
The bottom line: For blinds and shades, string and cord are the same thing. And whatever you call it, Blind Repair has it!

If there are Ideas/Questions you would like me to blog about comment below
For example:

• What is the differences between String and Cord?
• How do I know what size my Cord is?
• How much cord do I need to re-string my Venetian blind?