One cubic foot (12 x 12 x 12=1728 cubic inches) is equal to 7.48052 US gallons.
So, if your 65" wide TV was 26.584 inches high and 1 (one) inch deep it would have the equivalent of one cubic foot or hold 7.48052 gallons and weigh 62.4 pounds (just the water)
If my math is correct