FOREST PRODUCTS MEASUREMENTS
AND CONVERSION FACTORS:
With Special Emphasis on the U.S. Pacific Northwest
Copyright © 1994 by the College of Forest Resources, University
Printed in the United States of America
All rights reserved. No part of this publication may be reproduced
or transmitted in any form or by any means, electronic or mechanical,
including photography, recording, or any information storage or
retrieval system, without permission in writing from the publisher,
the College of Forest Resources.
Additional copies of this book may be purchased from the University
of Washington Institute of Forest Resources, AR-10, Seattle, Washington
Editing and Design: Leila Charbonneau
Word Processing: Margaret Lahde
Library of Congress Cataloging-in-Publication Data
Briggs, David George.
Forest products measurements and conversion factors : with special
emphasis on the U.S. Pacific Northwest / David Briggs.
p. cm. - (Institute of Forest Resources contribution ; no. 75)
Includes bibliographical references (p. ) and index.
1. Forest products-Northwest, Pacific-Measurement. 2. Forest products-Standards-Northwest,
Pacific. I. Title. II. Series: Contribution (University of Washington.
Institute of Forest Resources) ; no. 75.
1. Basic Wood
Properties: (For a printout or download, go to Chapter
of Logs: (For a printout or download, go to Chapter
3. Stacked Roundwood,
Preservative-Treated Products, and Construction Logs:
(For a printout or download, go to Chapter
4. Lumber: (For a printout or download, go to Chapter
5. Veneer and Plywood: (For a printout or download, go to Chapter
Panel Products: Particleboard, Hardboard, Medium Density Fiberboard,
OSB/Waferboard, and Insulation Board: (For a printout or download,
go to Chapter 6 pdf)
7. Chips, Sawdust,
Planer Shavings, Bark, and Hog Fuel: (For a printout or download,
go to Chapter 7 pdf)
8. Pulp and
Paper: (For a printout or download, go to Chapter
(For a printout or download, go to Chapter
and Shakes: (For a printout or download, go to Chapter
and Utilization of Trees: (For a printout or download, go to Chapter
Appendix 1. Conversions Between
Imperial and Metric Measures: (For a printout or download, go to Appendix
Appendix 2. Conversion Factors
for Wood Products: (For a printout or download, go to Appendix
Appendix 3. Board Foot Log
Rules: (For a printout or download, go to Appendix
Appendix 4. Scientific and
Common Names of Tree Species: (For a printout or download, go to Appendix
Appendix 5. Associations
and Grading Agencies: (For a printout or download, go to Appendix
Glossary: (For a printout or download, go to Glossary
References: (For a printout or download, go to References
Completion of this book would not have been possible without the
tremendous education and support given me by many practitioners
in the forest products industry and the numerous queries I have
received from people confused or troubled by some measurement or
conversion problem. This is an educational process that is ongoing.
The following were especially helpful in aiding with preparation
and review of various chapters:
Craig Adair, American Plywood Association
David Anderson, Graduate Research Assistant
Jack Eddy, Red Cedar Shingle and Handsplit Shake Bureau
Tom Fahey, USFS Pacific Northwest Research Station
Don Flora, USFS Pacific Northwest Research Station
Rick Gustafson, University of Washington
Denny Hill, Graduate Research Assistant
Kevin Hodgson, University of Washington
Robert Keller, Weyerhaeuser Company
Bruce Lines, Wyckoff Company
Les Lonning, L.D. McFarland Company
Tom Maloney, Washington State University
Bob Netro, L.D. McFarland Company
George Sleet, American Plywood Association
Ed Williston, Ed Williston Associates, Inc.
Sue Willits, USFS Pacific Northwest Research Station
Gerry Willits, U.S. Bureau of Land Management
Ken Wilson, Weyerhaeuser Company
My thanks also go to Tom Snellgrove, former Project Leader of the
Timber Quality Research Unit at the U.S. Forest Service Pacific
Northwest Research Station, who originally suggested that I do this
Development of this publication was supported by the U.S. Forest
Service Pacific Northwest Research Station Project 88-325, the University
of Washington Center for International Trade in Forest Products
(CINTRAFOR), the McIntire-Stennis Cooperative Forestry Research
Program, and the University of Washington College of Forest Resources.
Understanding forest products measurements is important to anyone
in the forest products industry. Converting volume, area, lineal,
or weight measurements between the metric and Imperial systems is
not as simple or straightforward as it would seem. Incorrect, obsolete,
and ambiguous conversion factors can be very misleading and may
result in large errors. Some reasons for this are:
1. Lack of standardization as to how measurements are taken and
recorded. For example, logs may have diameter taken at one end,
both ends, or at midlength; the measure may be inside or outside
bark, and may be recorded to the nearest tenth, nearest inch or
centimeter, or with the fraction dropped.
2. Even if the same measurements are recorded, they may be entered
into different formulas that yield different results. Various cubic
log volume formulas yield different results even when the same log
measurements are used. Often, log scaling systems differ both in
the way measurements are taken and in the formula used.
3. The units for expressing volume or weight are often different
and may not be clearly defined. Log volume may be expressed in cubic
feet, cubic meters, board feet, koku, and so forth. A ton of chips
may be wet or bone dry and may be a short ton, long ton, or metric
tonne. Chips are also expressed as units and bone-dry units.
4. Even if the same unit of measurement is used, it may not represent
the same quantity. A good example is the difference between a board
foot in log scaling and a board foot in tallying lumber at a sawmill.
5. Correct conversion factors for some products, such as logs and
lumber, vary with piece size.
6. Wood is variable. Wood density-the measure of mass of wood per
unit volume-varies between species, between trees of the same species,
and between parts of the same tree. Wood moisture content can vary
from a few percent to more than half the weight of a piece. Since
wood shrinks and swells as moisture content changes, these changes
affect volume as well as weight. Many wood product measurements
and conversion factors that are reported are ambiguous because no
indication of such conditions is given.
While this book primarily focuses on forest products in the Pacific
Northwest, several national and foreign systems are included because
of the rapid globalization of markets. Because many readers may
be relatively new to the industry and its terminology, a glossary
is provided and descriptive background on the philosophy and assumptions
that underlie formulas and measurement systems is presented. Procedures
and illustrative examples are emphasized to encourage the reader
to gather and use local information rather than rely on tables of
averages. With the ready availability of computers and software
packages, the focus on procedures is appropriate to enable readers
to develop software to perform calculations they need. Tabulated
species and regional averages are also presented. These values can
be used as a rough check on calculations or as an approximation
if local data are not available. The reader should be cautioned
that tabled averages may be based on limited samples, so conversion
factors calculated from these tables may differ substantially from
the local reality.
Although the examples were taken from actual situations, they should
not be regarded as representative of the current forest resource
or average industry practice. They were chosen to illustrate and
reinforce the calculation methods, to provide insights on how systems
attempting to measure the same product vary, and why some are less
consistent or more biased than others.
The appendixes provide tables of standard conversion between Imperial
and metric measures, conversion factors used by the U.S. Forest
Service in its latest assessment of the U.S. timber situation (Haynes
1990), some examples of board foot log rules, common and scientific
names of U.S. tree species, and names of industry associations for
products discussed in this book.
Information on the physical and mechanical properties of commercially
important species, along with descriptions of products, processes,
and grades, can be found in the Wood Handbook (USFS 1987), which
is recommended as a companion to this volume. It is available through
the U.S. Government Printing Office.
Unlike previous editions, this version does not contain forestry
yield tables, site curves, and so forth. This and other forestry
information is well covered in Log Scaling and Timber Cruising,
by J.F. Bell and J.R. Dilworth, available through the Oregon State
University Press, Corvallis.
Readers are encouraged to send the author descriptions of measurement
systems and conversion factors not covered in this edition. These
inputs will be valuable in expanding the scope of future editions
to include more foreign country systems as the forest products industry
continues its globalizing trend.