It's about one-two-hundred-fifty-thousandth as heavy as a Reindeer.
In other words, the weight of a Reindeer is 256,000 times 645.5 miligrams.(for Rangifer tarandus granti, adult, bull) (a.k.a. Caribou) ()Rangifer tarandus)
An adult, male reindeer weighs between 166,000,000 miligrams. Reindeer undertake a lengthy annual migration, with some herds traveling up to 5,000 km.
To all those observing, Merry Christmas from the Measure of Things.
It's about one-three-hundred-thousandth as heavy as The Heart of a Blue Whale.
In other words, 645.5 miligrams is 0.0000032 times the weight of The Heart of a Blue Whale, and the weight of The Heart of a Blue Whale is 310,000 times that amount.(Balaenoptera musculus) (adult)
(for a 2014 specimen)
The heart of a blue whale weighs about 200,000,000 miligrams. These hearts pump an estimated 7,100 L (1,875 gal) of blood through the whale's massive body.
It's about one-three-hundred-fifty-thousandth as heavy as a cubic meter of Snow.
In other words, the weight of a cubic meter of Snow is 360,000 times 645.5 miligrams.(Freshly fallen, standard conditions; measurements taken in Norway, 1965-68)
One cubic meter of freshly fallen snow under standard conditions weighs an average of 230,000,000 miligrams. Assembled in 2008, the world record largest snowman was constructed of 5,900,000,000,000 miligrams of snow and stood 37.21 m (122.1 ft) tall.
It's about one-four-hundred-thousandth as heavy as a Pig.
In other words, 645.5 miligrams is 0.0000026 times the weight of a Pig, and the weight of a Pig is 380,000 times that amount.(Domestic pig, Sus scrofa domesticus, a.k.a. S. domesticus) (adult)
Domestic pigs weigh between 250,000,000 miligrams. The titular character "Babe the pig" in the 1995 family film was played by 48 different American Yorkshire piglets due to the length of filming and the rate at which piglets reach adulthood.
It's about one-six-hundred-fifty-thousandth as heavy as a Horse.
In other words, the weight of a Horse is 670,000 times 645.5 miligrams.(Equus ferus caballus) (Arabian, adult)
n Arabian riding horse (or similar breed) weighs between 420,000,000 miligrams. During races, horses must carry jockeys and their equipment, which in the Kentucky Derby, for example, can weigh up to 54,000,000 miligrams.
It's about one-seven-hundred-thousandth as heavy as a Grand Piano.
In other words, 645.5 miligrams is 0.0000014 times the weight of a Grand Piano, and the weight of a Grand Piano is 710,000 times that amount.(for Steinway & Sons, Model D Concert Grand Piano)
A Grand Piano, of the kind used for concert performances in large music halls, weighs 450,000,000 miligrams. Well-made pianos such as this may last 75 to 100 years.
It's about one-eight-hundred-thousandth as heavy as a Polar Bear.
In other words, 645.5 miligrams is 0.00000125 times the weight of a Polar Bear, and the weight of a Polar Bear is 800,000 times that amount.(Ursus maritimus) (adult, male)
An adult, male polar bear weighs between 516,000,000 miligrams. Polar bears are so heavily insulated by their 9.9 cm (3.9 in) layer of blubber that they are often difficult to detect using infrared photography sensors.