Calculating the weight of paper requires the Basis Weight or M-Weight of the paper.

The M-Weight (MWT) is the actual weight of 1000 sheets of a particular size. If a sheet is cut in half, the MWT is also halved.

The basis weight (BWT) is the actual weight of 500 sheets (a ream) of the basic sheet size. The basic sheet size depends on the grade of paper. If a sheet is cut in half, the BWT remains the same.

80# Text = 500 sheets of 25 x 38 will weigh 80 pounds

80# Cover = 500 sheets of 20 x 26 will weigh 80 pounds

Here is a listing of commonly used paper grades and their basic sheet sizes:

Grade | Basic Size | Sq In (BSQ) | |

Board | 22 x 28 | 616 | |

Bond | 17 x 22 | 374 | |

Book | 25 x 38 | 950 | |

C1S/C2S Cover | 24 x 36 | 864 | |

Cover | 20 x 26 | 520 | |

Index | 25.5 x 30.5 | 778 | |

NCR | 17 x 22 | 374 | |

Newsprint | 24 x 36 | 864 | |

Offset | 25 x 38 | 950 | |

Opaque | 25 x 38 | 950 | |

Tag | 22.5 x 28.5 | 642 | |

Text | 25 x 38 | 950 | |

Vellum Bristol | 22.5 x 28.5 | 642 | |

Writing | 17 x 22 | 374 |

When the M-Weight (MWT), Basis Weight (BWT) and Sheet Size are known, the BSQ can be calculated using the following formula:

BSQ = ( 2 / (MWT/BWT) ) * Size

MWT = (BWT * Size * 2) / BSQ

BWT = (BSQ * MWT) / (Size * 2)

Note: Envelopes don't generally have a basic size. For estimating purposes we recommend using 475 square inches.

Note: Envelopes don't generally have a basic size. For estimating purposes we recommend using 475 square inches.