You should be able to figure it out pretty easily. 1" steel weighs 40lbs. a square foot, 1/2" weighs 20lbs. a square foot, 1/4" weighs 10lbs. and so on.
All you need to do is measure the blade thickness and number of square feet and then do a little math. You will be very close. Don't forget all of the brackets, braces, etc.