It's about one-five-hundred-fiftieth as heavy as a Can of Soup.
In other words, the weight of a Can of Soup is 560 times 645.5 miligrams.(for Campbell''s Condensed Tomato Soup, 317.9 ml)
A can of Campbell''s Tomato Soup weighs 350,000 miligrams. Cans have been used to store soup and other foods since their invention in 1913, but a dedicated can opener was not developed until cans began to use thinner materials — prior to that time, cans were usually opened using various blunt instruments and tools.
It's about one-six-hundred-fiftieth as heavy as a Football (American).
In other words, 645.5 miligrams is 0.001570299478514 times the weight of a Football (American), and the weight of a Football (American) is 636.8212011038 times that amount.(a.k.a. "pigskin") (NFL standard)
Per National Football League official rules, an American football must weigh between 396,893.32375 miligrams and 425,242.846875 miligrams. Because of NFL regulations, ceremonial considerations, and backup requirements, each NFL Superbowl requires the manufacture of 144 balls exclusively for the event.
It's about one-six-hundred-fiftieth as heavy as a Football (Soccer).
In other words, the weight of a Football (Soccer) is 670 times 645.5 miligrams.(a.k.a. Soccer, a.k.a. Association Football) (FIFA Law 2 specification)
According to FIFA's Law of the Game number 2, a football must weigh between 410,000 miligrams and 450,000 miligrams. An artifact on display at the Smith Art Gallery in Museum in Stirling, Scotland is said to be the world's oldest football and is about one-third to one-half the size of a modern football.
It's about one-nine-hundred-fiftieth as heavy as a Basketball.
In other words, 645.5 miligrams is 0.0010349701108 times the weight of a Basketball, and the weight of a Basketball is 966.21147757 times that amount.(NBA official ball standards, Size 7)
A regulation NBA basketball, manufactured by Spalding, is known as a Size 7 ball and weighs 623,689.50875 miligrams. These balls have 4,118 pebbles each with a diameter of 2.5 mm
It's about 1,000 times as heavy as a Grain of Sugar.
In other words, 645.5 miligrams is 1,030 times the weight of a Grain of Sugar, and the weight of a Grain of Sugar is 0.000971 times that amount.(a.k.a. white sugar, a.k.a. white refined sugar, a.k.a. table sugar, a.k.a. sucrose, a.k.a. saccharose)
A grain of sugar weighs approximately 0.625 mg. Sugar consumption varies widely by country; the average citizen of the United States consumes about 61,200,000 miligrams of sugar each year.
It's about one-one-thousand-five-hundredth as heavy as a liter of Water.
In other words, 645.5 miligrams is 0.0006454819 times the weight of a liter of Water, and the weight of a liter of Water is 1,549.23 times that amount.(fresh; 4° C / 39.2° F; maximum density)
Contrary to popular belief, 1 liter (0.0.264172052358148 gal) of water at 4° C / 39.2° F (its point of maximum density) weighs 1,000,028 miligrams rather than 1 kg exactly. The total volume of water on the planet Earth is about 13,590,000,000,000,000,000 (13.59 quntillion) L (3,590,000,000,000,000,000 gallons).
It's about one-two-thousandth as heavy as a Human Brain.
In other words, 645.5 miligrams is 0.000478 times the weight of a Human Brain, and the weight of a Human Brain is 2,090 times that amount.(adult)
The average weight of an adult human brain is between 1,350,000 miligrams. In humans and primates, sight and vision utilize about 30 different parts of the brain which together account for about half of the brain's size.