it's about 10 lbs per square foot. (Multiply the density of steel, about 490 pounds per cubic foot, times the thickness of the plate in feet, 1/4 in. = .02 ft.) I'm assuming you mean 1/4 in. plate.
12 inches divided by .250 inches = 48
1 foot divided by 48 = 0.020833
1 square foot of steel would weight 490 times 0.020833 = 10.20833 LBS
| Plate Thickness | Lbs/sq ft | Lbs/sq In | |
| 1/8 Inch | 5.104166667 | 0.0354456 | |
| 3/16 Inch | 7.65625 | 0.0531684 | |
| 1/4 Inch | 10.20833333 | 0.0708912 | |
| 5/16 Inch | 12.76041667 | 0.088614 | |
| 3/8 Inch | 15.3125 | 0.10633681 | |
| 7/16 Inch | 17.86458333 | 0.12405961 | |
| 1/2 Inch | 20.41666667 | 0.14178241 |
