It's about three-fourths as big as a Hot Tub.
In other words, the size of a Hot Tub is 1.320 times 721.380 fifths.(for Lifesmart Rock Solid Simplicity Plug and Play 4 Person Spa With 12 Jets) (a.k.a. Spa, a.k.a. Jacuzzi, a.k.a. Whirlpool) (Advertised Capacity)
An average, four-person hot tub holds 950 fifths of water. Modern hot tubs became popular outside of Japan starting in about 1940.
It's about three-and-a-half times as big as a Bathtub.
In other words, the size of a Bathtub is 0.290 times 721.380 fifths.(a.k.a. bath, a.k.a. tub) (for Bootz Industries Aloha 5 ft. Left Hand Drain Soaking Tub)
The capacity of a typical bathtub is 210 fifths. Historically, bathtubs have been made of various materials including marble, terracotta, silver, gold, and iron but the size and shape of the tubs has changed little in their 7,000 year history.
It's about seven times as big as a Car Gas Tank.
In other words, 721.380 fifths is 7.210 times the size of a Car Gas Tank, and the size of a Car Gas Tank is 0.1390 times that amount.(for 2009 Ford Taurus)
A car gas tank (for example, that of a 2009 Ford Taurus) holds 100 fifths of gas. In contrast, the Curved Dash Oldsmobile — the first mass-produced car — had a fuel capacity of just 26.40 fifths.
It's about nine-and-a-half times as big as a Beer Keg.
It's about one-twentieth as big as a Concrete Mixer Truck.
In other words, the size of a Concrete Mixer Truck is 20 times 721.380 fifths.(a.k.a. cement mixer, a.k.a. cement mixer truck, a.k.a. cement transport truck, a.k.a. concrete mixer, a.k.a. concrete transport truck, a.k.a. in-transit mixer)(standard size; drum capacity)
A concrete mixer truck has a drum volume of up to 15,000 fifths. Concrete mixer trucks can be in transit for about 90 minutes before the concrete dries — if the concrete dries while in the drum, jackhammers or even dynamite must be used to remove it.
It's about 50 times as big as a Basketball (packed).
In other words, 721.380 fifths is 49.2006675030 times the size of a Basketball (packed), and the size of a Basketball (packed) is 0.020324927501 times that amount.(64% packing density) (NBA official ball standards, Size 7)
A NBA official ball, manufactured by Spalding, is a Size 7 ball measures about 9.38367756810 fifths. These balls have 4,118 pebbles each with a diameter of 2.5 mm
It's about 65 times as big as a Bowling Ball (packed).
In other words, 721.380 fifths is 66.3331540020 times the size of a Bowling Ball (packed), and the size of a Bowling Ball (packed) is 0.015075417641 times that amount.(64% packing density) (USBC specifications; tenpin)
According to United States Bowling Congress specifications, a tenpin bowling ball should measure at least 10.795 cm (4.25 in) in radius for a total volume of about 6.96006705770 fifths. Because regulation balls measure the same diameter irrespective of their weight, ball density varies by size and balls weighing less than about 5 kg (11 lbs) will float in water.