It's about four-fifths as heavy as a Nail.
In other words, 645.5 miligrams is 0.82 times the weight of a Nail, and the weight of a Nail is 1.2 times that amount.(for 15-gauge, 2-inch, finishing nails)
A two-inch finishing nail weighs 790 miligrams. Nails have been in use for more than 5,400 years and were ven used as a medium of exchange in ancient times.
It's about three-fifths as heavy as a Jelly Bean.
In other words, 645.5 miligrams is 0.59 times the weight of a Jelly Bean, and the weight of a Jelly Bean is 1.7 times that amount.(for Jelly Belly beans; approximate)
Made of sugar, corn syrup, and pectin, a single jelly bean weighs about 1,100 miligrams. President Ronald Reagan cited jelly beans as his favorite candy and 3,200,000,000 miligrams of the candies were served at his first inauguration in 1981.
It's about half as heavy as a Paper Clip.
In other words, 645.5 miligrams is 0.46 times the weight of a Paper Clip, and the weight of a Paper Clip is 2.2 times that amount.(average)
Notwithstanding the tremendous variation in sizes and materials, a typical paperclip weighs about 1,400 miligrams. The country of Norway has used the paper clip as something of a national symbol since the end of World War II based on the erroneous notion that the paperclip was invented by a Norwegian, Johan Vaaler. However, the paperclip had already been in existence for at least 30 years by the time of Vaaler patented his paperclip design.
It's about one-third as heavy as a Playing Card.
In other words, the weight of a Playing Card is 2.8 times 645.5 miligrams.(ISO 216 B8 size, 2.5" x 3.5")
A single ISO 216 B8-size playing card weighs 1,800 miligrams. Although this size is the most common home playing card, many casinos use "bridge size" cards — 2,640 sq. mm (4.036 sq. in) smaller in area.
It's about three times as heavy as a Raindrop.
In other words, the weight of a Raindrop is 0.3 times 645.5 miligrams.(a.k.a. drop, a.k.a. droplet) (average)
The weight of a raindrop depends heavily on the type of weather, but averages about 200 mg. The familiar teardrop shape of a raindrop is actually an optical illusion, caused by the reflection of the light and the motion of the drop.
It's about one-fourth as heavy as a Penny.
In other words, 645.5 miligrams is 0.26 times the weight of a Penny, and the weight of a Penny is 3.8 times that amount.(United States) (formally one-cent coin) (Union shield design, 2010-present)
The weight of a United States penny is 2,500 miligrams. According to a 2010 report by the United States Mint, the cost of manufacturing and distributing a penny is $0.0179 — more than its face-value.
It's about one-fifth as heavy as a Die (Dice).
In other words, 645.5 miligrams is 0.16 times the weight of a Die (Dice), and the weight of a Die (Dice) is 6.3 times that amount.(for six-sided, 16 mm, rounded cube)
A die, of the size most commonly used in board games and casinos, typically weight 4,100 miligrams. The use of dice and dice-like tools predates written history, with the oldest known examples belonging to a 5,000-year old backgammon set uncovered during an archaeological dig in modern-day Iran.