What | The basis weight of paper, board or corrugated board in g/m² |

Why |
A constant weight contributes to consistency. This value is of importance when choices for means of distribution have to be made (mail or otherwise) and is also needed to interpret other physical properties that are specified with regard to weight. |

How |
On an analytical balance weighing of 10 samples of 100 cm². Optional: weighing at least 10 samples of known area (e.g. 210x297 mm=A4) and calculating the weight in g/m². |

Calculations |
Where: Report the average of at least 10 significant values and the standard deviation. |

Thickness (ISO 534, TAPPI T411, ISO 3034):

What | The distance between front and back of a single sheet of paper, board or corrugated board, expressed in µm (1 micrometre = 0.001 mm) |

Why |
Variation in thickness causes variation in the printed image and may be of influence on certain finishing processes. |

How |
20 Measurements in micrometres with a conforming thickness gauge. Another way of measuring thickness is to measure the total thickness of a stack of 10 sheets on 5 specified places. Average results divided by 10. This is often referred to as bulking thickness as opposed to single sheet thickness. (Official ISO standard is withdrawn.) |

Calculations |
Where: Report the average of at least 10 significant values and the standard deviation. |

What | This is the ratio between thickness and weight, the specific volume, expressed in cm³/g. A higher value indicates a higher bulk. |

Why |
Bulk of paper is e.g. used to determine the total thickness of a book or magazine. |

How | Measuring both weight and thickness as described, calculating the bulk. |

Calculations |
Report the average of at least 10 significant values and the standard deviation. |

Mass Density (ISO 534, TAPPI T411):

What | To show how much mass is present in a specific volume, expressed in g/cm³. |

Why | Density has impact on opacity and strength properties. |

How | Measuring both weight and thickness as described, calculating the mass. |

Calculations |
Report the average of at least 10 significant values and the standard deviation. |