Safe bet...unless there is no decor in the tank, nor equipment, plants, gravel, substrate, or maybe even fish...and the glass might have to be shaved a little bit on the inside, too!
Of course you have to take into account you wont fill it right up, and the thickness of the glass should be subtracted - unless you measured from the inside. And, as mentioned, displacement from decor and as such would reduce the water volume. And then the equipment take up space, which will reduce a small amount of volume...in the end we're not left with much! lol.
However, they usually sell the tanks by outside dimensions. It is not unusual for a 55 to turn into a 47 just using the inside dimensions, no fish, no decorations, just water