Check your sample cutter by yourself with a simple method .Cut a white page and fold it and measure by mm steel ruler . If it is 112.6 mm and above then your cutter is ok to get accurate result .
The area of a circle is calculated by multiplying the square of the radius by π (3.141592...)
So if the diameter is 113 mm, the radius will be 113/2 = 56.5. The area of the specimen you cut will therefore be 56.5 x 56.5 x 3.141592 = 100.29 sq cms.
You are looking for Grams per Square Meter. The area of 1 square metre is 100 x 100 square cms = 10,000 sq cms.
Therefore if you divide 10,000 by the area of the specimen you have cut, you will get,
10,000 / 100.29
= a factor of 99.71.
Therefore if you multiply the weight of the specimen by 99.71 you will get the Grams per Square Meter. Most people multiply by 100, so, when they read the result from the balance they automatically just move the decimal point two places to the left.
As an illustration suppose the specimen weights 1.85grams, the GSM will be 1.85 x 100 = 185 grams per square metre.
If you multiplied by 99.71 the result would be 1.85 x 99.71 = 184.46 grams per square metre.
Because of variations in the cutting performance of different fabrics the O.29grams does not really play a significant role in the accuracy of the test result and most performance requirements anyway give a tolerance of maybe +- 2/3%.
