Paper calculation

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Standard methods to calculate paper and board characteristics require the use of the International System of Units (SI or SI metric units).

CALCULATING PAPER

Details of SI are provided in the ISO Standards 31:1981 and 1000:1981. Some quantities can be expressed in different SI units. Such variations can lead to confusion in reporting test results and quoting property values.

In order to overcome such problems within the pulp, paper, and paperboard field, ISO/TC6 has recommended appropriate units in ISO Standard 5651:1989 (E). There is also a very useful recommended practice issued by Tappi (T 1210 sp-93), which deals with the application of the International System of Units.

WEIGHT IN KG OF A GIVEN NUMBER OF SHEETS

Weight = L x Swd x Gsm x Ns / 1000

L = Length of sheet in metres
Swd = Width of sheet in metres
Gsm = g/m² of paper
Ns = Number of sheets

GRAMMAGE OF A SHEET OF PAPER IN G/M2

Grammage = W x 1000 / L x Swd x Ns

W = Weight in kg
L = Length of sheet in metres
Swd = Width of sheet in metres
Ns = Number of sheets

NUMBER OF SHEETS FOR A JOB

Total = Npj x Cr x (100 + %overs) / Nps x 100

Npj = Number of printed pages of job
Cr = Copies required
Nps = Number of printed pages per sheet

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