Bathtubs are available in many sizes, a typical size being 30 inches wide and 60 inches long. The inside measurements of this tub could be 23 inches wide, 15 inches deep to the water level and 54 inches long. This tub holds about 80 gallons of water. If this is an extra deep tub, it might hold up to 110 gallons. A very small bathtub might hold 40 gallons, while a larger single person bathtub could easily hold 100 gallons or more. My bath tub holds 110 gallons (pictured above), and my 50 gallon water heater couldn’t even fill it with enough hot water to use the whirlpool jets. According to Alliance For Water Efficiency, a standard non-jetted bathtub holds between 25 and 45 gallons of water approximately. The average elongated bathtub in North America holds 58 gallons of water. Corner tubs hold more and freestanding tubs slightly less. The average bathtub size has changed tremendously over the last decade. The 30 to 50 gallons average volume is for a tub that is half full to Spa Volume Calculator. How to Calculate Hot Tub Volume in Gallons. Proper water treatment and hot tub maintenance are dependent on the size of your hot tub Average-Bathtub-Volume On average, a standard tub will hold between 30 to 50 gallons of water when it is half filled to leave room for The standard bathtub, which measures 60 inches long by 30 inches wide, holds The tub’s volume, in gallons, is then determined by multiplying the total Most people use about 30 gallons of water for a bath, according to industry estimates. When filled to capacity (just below the overflow), a standard bathtub holds 42 gallons, but some of that water will be displaced when you get into the tub. Plumbing and Piping – volume of bathtub – How do I figure out how many gallons of water my custom designed bathtub will hold? In other words, the size of a Bathtub is 0.830 times 50 gallons. common keg size sold by US beer sellers is a half-barrel type with a volume of 15.50 gallons.