| Source: | FP-14 Standard Specifications |
| Author: | FHWA |
| Class | % of Rock Equal or Smaller by Count | Range of Intermediate Dimensions,(2) | Range of Rock Mass,(3) |
|---|---|---|---|
| DX | inches (millimeters) | pounds (kilograms) | |
| 1 | 100 | 9 – 15 (230 – 380) | 59 – 270 (27 – 120) |
| 85 | 7 – 11 (180 – 280) | 28 – 110 (13 – 50) | |
| 50 | 5 – 8 (130 – 200) | 10 – 42 (5 – 19) | |
| 15 | 3 – 6 (80 – 150) | 2 – 18 (1 – 8) | |
| 2 | 100 | 15 – 21 (380 – 530) | 270 – 750 (120 – 340) |
| 85 | 11 – 15 (280 – 380) | 110 – 270 (50 – 120) | |
| 50 | 8 – 11 (200 – 280) | 42 – 110 (19 – 50) | |
| 15 | 6 – 8 (130 – 200) | 10 – 42 (6 – 19) | |
| 3 | 100 | 21 – 27 (530 – 690) | 750 – 1600 (340 – 730) |
| 85 | 15 – 19 (380 – 480) | 270 – 560 (120 – 250) | |
| 50 | 11 – 14 (280 – 360) | 110 – 220 (50 – 100) | |
| 15 | 8 – 10 (200 – 250) | 42 – 81 (19 – 37) | |
| 4 | 100 | 27 – 33 (690 – 840) | 1600 – 2900 (730 – 1300) |
| 85 | 19 – 23 (480 – 580) | 560 – 990 (250 – 450) | |
| 50 | 14 – 17 (360 – 430) | 220 – 400 (100 – 180) | |
| 15 | 9 – 12 (230 – 300) | 59 – 140 (27 – 64) | |
| 5 | 100 | 33 – 39 (840 – 990) | 2900 – 4850 (1300 – 2200) |
| 85 | 23 – 28 (580 – 710) | 990 – 1800 (450 – 820) | |
| 50 | 17 – 20 (430 – 510) | 400 – 650 (180 – 290) | |
| 15 | 11 – 15 (280 – 380) | 110 – 270 (50 – 120) | |
| 6 | 100 | 39 – 45 (990 – 1140) | 4850 – 7400 (2200 – 3350) |
| 85 | 28 – 32 (710 – 810) | 1800 – 2650 (820 – 1200) | |
| 50 | 20 – 23 (510 – 580) | 650 – 990 (290 – 450) | |
| 15 | 13 – 17 (330 – 430) | 180 – 400 (82 – 180) | |
| 7 | 100 | 45 – 54 (1140 – 1370) | 7400 – 12,800 (3350 – 5800) |
| 85 | 32 – 38 (810 – 970) | 2650 – 4450 (1200 – 2000) | |
| 50 | 23 – 28 (580 – 710) | 990 – 1800 (450 – 820) | |
| 15 | 15 – 20 (380 – 510) | 270 – 650 (120 – 290) | |
| 8 | 100 | 54 – 66 (1370 – 1680) | 12,800 – 23,400 (5800 – 10,600) |
| 85 | 38 – 47 (970 – 1190) | 4450 – 8450 (2000 – 3850) | |
| 50 | 28 – 35 (710 – 890) | 1800 – 3500 (820 – 1600) | |
| 15 | 19 – 25 (480 – 640) | 560 – 250 (250 – 570) | |
| 9 | 100 | 66 – 78 (1680 – 1980) | 23,400 – 38,600 (10,600 – 17,500) |
| 85 | 47 – 55 (1190 – 1400) | 8450 – 13,500 (3850 – 6100) | |
| 50 | 35 – 41 (890 – 1040) | 3500 – 5600 (1600 – 2550) | |
| 15 | 22 – 30 (560 – 760) | 870 – 2200 (390 – 1000) | |
| 10 | 100 | 78 – 90 (1980 – 2290) | 38,600 – 59,300 (17,500 – 26,900) |
| 85 | 55 – 64 (1400 – 1630) | 13,500 – 21,300 (6100 – 9650) | |
| 50 | 41 – 48 (1040 – 1220) | 5600 – 9000 (2550 – 4100) | |
| 15 | 26 – 36 (660 – 910) | 1450 – 3800 (660 – 1700) | |
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(1) Gradation includes spalls and rock fragments to provide a stable, dense mass.
(2) The intermediate dimension is the longest straight-line distance across the rock that is perpendicular to the rock’s longest axis on the rock face with the largest projection plane.
(3) Rock mass is based on a specific gravity of 2.65 and 85 percent of the cubic volume as calculated using the intermediate dimension.
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