How many feet by how many feet in 450 sq meters?

To Convert Sq. Metres(Metric) to Sq. Feet(Imperial) Multiply by 10.7639

Hence, 450 Sq. Metres = 450 * 10.7639 = 4843.755 Sq. Feet

That would be a square of 69' 7 5/32" long by 69' 7 5/32" wide.