CONTENTS 



Page 



CONVERSION FACTORS, U.S. CUSTOMARY TO METRIC (SI) ... . 5 



SYMBOLS AND DEFINITIONS 6 



I INTRODUCTION 7 



II GRADE SCALES 7 



1 . Background 7 



2. Common Classification Schemes 8 



III PHI NOTATION 8 



1. Background 8 



2. Phi Grade Scale 10 



3. Terminology and Use 15 



4. Conversions 16 



IV EXAMPLE CALCULATIONS 16 



LITERATURE CITED 18 



TABLES 



1 Grain-size scales--soil classification 9 



2 Weight percentages by class of two typical beach sands .... 17 



3 Phi sizes and millimeter equivalents of the phi mean for 



the grain-size distribution data shown in Table 2 17 



FIGURES 



1 Cumulative size-frequency plots comparing (a) millimeter 



and (b) phi-size scales 10 



2 Size-frequency plots comparing (a) millimeter versus 



(b) phi-size scales 11 



3 The normal curve (for y = 2.0, o = 0.70) '. . . . 13 



4 Cumulative size frequencies on phi probability plot 14 



