how to convert 90 grams per square meters in bed sheets to US thread count

Question

if the answer is 90 grams per square meters, as it is written in bed sheets, what does that mean in US thread count.  I've been told what "thread count" means, the number of threads counted in a square inch, but I don't know how to convert meters to inches.  When I look for new bed sheets from a seller, like Macy's, they tell me that the sheets have a thread count of 200, or 300, or 400, or more, which they say means that the sheets have a higher thread count the larger the number gets, making for a better quality bed sheet, or so they tell me.  I'm trying to purchase bed sheets in Missouri, but the sheets they are advertising shows 90 GSM, instead of a thread count.  I'm not able to calculate 90 GSM into a US thread count.  When I see 90 GSM, I'm trying to change that to a US bed sheet thread count.  In my brain, I just can't convert grams per square meter into US inches in thread count.  I've had 5 strokes, I haven't been able to do math for a long time.  I know how to ask myself a question, but I don't know how to get the answer from my brain when trying to calculate a math question for myself.  I can do a simple 2 plus 2 means 4, but I can't tell you what 26 minus 17 means unless I use a calculator.  I do know how to ask questions, but I have no way of knowing if my answer is correct unless someone tells me.  I just can't do that.  I'm sorry to bother you, but I really need your help for what should be something so simple to do.  can you help, please?  I use a computer to help myself get through life, which is such a plus, and I know how to ask a math question online, though it was really difficult to find someone that could just give me a simple answer.  Every where I've look online, they all want to give the equation, but not the answer.  Then I found you.  I don't know how to make equations work in my brain, if you give me an equation, I have no way of knowing what it means when I read it.  I don't know what most of the symbols mean, and even if I could read them, they don't means anything to me.  Thanks for listening to me.   Mike Haggard - mike22mike@gmail.com

Answer 1

There are 2.54cm to an inch. There are 100cm in a metre, so 2.54cm is 2.54/100=0.0254m. That means 1m=39.37in approx. But we want square inches and square metres, so 1 sq m=39.37²=1550 sq in approx.

From your information we know that thread counts are the number of threads in a square inch. So 1 sq m would contain 1550 times the thread count.

A thread count of 200 would mean 200×1550=310000 threads per sq m, or threads/m².

A thread count of 300 is 465000 threads/m² and 400 is 620000 threads/m².

We don’t know the mass of a single thread so we don’t know which of 200, 300, or 400 is equivalent to 90gsm. The weight or mass of a single thread will be very small of course, and, in theory, to measure it you would need to get 1m length threads and lay them side by side (in a lattice) until you have a metre’s width. Then you would weigh the threads. But for a thread count you would only need to find out how many threads side by side (in a lattice) will make up a square inch, regardless of their length, because you’re not measuring their combined mass.

So the two measurements are not compatible because one is a weight or mass and the other a simple number, a count. Therefore, knowing how to convert square inches into square metres is not going to help you in this case.

The only certain way to find out the equivalent of GSM and US thread count is to do what you did and enquire! For now, I would simply assume that 300TC is equivalent to 90gsm, because 300TC is probably the most popular measure.

If you have the TC, you find GSM by multiplying the thread count by 3 then divide by 10; if you have the GSM you find TC by multiplying the GSM by 10 then divide by 3. So 200TC would be 60gsm and 400TC would be 120gsm.

I hope this helps. You should find that 90-110gsm is the normal range for bed sheets.