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