| Equiv. Round Size (in) | Min. Rise (in) | Min. Span (in) | Wall (in) | Water-Way Area (sq-ft) | LB/FT |
|---|---|---|---|---|---|
| 15 | 11 | 18 | 2-1/4 | 1.1 | — |
| 18 | 13-1/2 | 22 | 2-1/2 | 1.65 | 170 |
| 21 | 15-1/2 | 26 | 2-3/4 | 2.2 | 225 |
| 24 | 18 | 28-1/2 | 3 | 2.8 | 320 |
| 30 | 22-1/2 | 36-1/4 | 3-1/2 | 4.4 | 450 |
| 36 | 26-5/8 | 43-3/4 | 4 | 6.4 | 595 |
| 42 | 31-5/16 | 51-1/8 | 4-1/2 | 8.8 | 740 |
| 48 | 36 | 58-1/2 | 5 | 11.4 | 880 |
| 54 | 40 | 65 | 5-1/2 | 14.3 | 1090 |
| 60 | 45 | 73 | 6 | 17.7 | 1320 |
| 72 | 54 | 88 | 7 | 25.6 | 1840 |
| 84 | 62 | 102 | 8 | 34.6 | 2520 |
| 90 | 72 | 115 | 8-1/2 | 44.5 | 2750 |
| 96 | 77-1/4 | 122 | 9 | 51.7 | 3110 |
| 108 | 87-1/8 | 138 | 10 | 66.0 | 3850 |
| 120 | 96-7/8 | 154 | 11 | 81.8 | 5040 |
| 132 | 106-1/2 | 168-3/4 | 10 | 99.1 | 5220 |
These tables are based on concrete weighing 150 pounds per cubic foot and will vary with heavier or lighter weight concrete.