For a very long time, since the beginning of coins about 2,600 years ago, coins have usually been round. But why? Why are coins round? Here are 7 reasons and theories that explain why a coin is typically round.

Melted metal moves like water, in drops, and splats flat like rain on a sidewalk. Thus the first melted metal coins were roundish in shape due to fluid mechanics.
Metal rods were easier to manufacture than flat sheet metal in ye olden days. Clipping the end of a metal rod produced a planchet that was then hit with a hammer that squished the planchet flat. Ta-da! Coins! The hammer blow worked in the same way on the planchet as gravity worked on melted metal, producing a similar circular shape. Although not perfectly round, these coins were just as circular as the melted metal droplets they replaced.
It is easier to see if a round coin has been modified. Clipped coins are easy to spot when they look like a circle with a flat side, however, if you clip the edge off of a rectangle, then you still have a rectangle. Circle shapes prevented this kind of clipping from flying under the radar.
Circles do not have corners to wear off. The smooth curve along the edge of a circle is more durable than a sharp corner so circle coins hold up better in circulation than square coins.
Round coins are less likely to poke people when carried in pockets, purses, or threaded on leather thongs and worn like necklaces, which were totally the first coin pendants…
Disks roll and stack on their own. This movement is useful in coin-operated machines. Some vending machines take advantage of the physics of a disk to sort and stack coins by denomination for easy collection.
Old habits die hard. A metal disk with markings on it is universally recognized as an item of value. A 2,600-year-old habit is hard to break!

There are exceptions to the round coin rule. Not all coins are round flat circles of metal. The following image shows six modern coins, none of which are round. Modern coins that are not round are popular with coin collectors.

20 pence UK 1986 coin.
5 mils Malta 1972 coin.
50 cent Jamaica 1981 coin.
15 cent Bahamas 1981 coin.
50 pence Ireland 1988 coin.
10 cent Bahama 1974 coin.

Historically, money has come in all different shapes and sizes. Before coins were universal, these non-round items were used just like coins.

Clamshells called Wampum were the preferred money in the Americas.
Cowrie shells served as coins in Asia, the Indian sub-continent, and Africa.
Iron money slowly replaced shells as the Iron Age progressed. Hoes, the gardening tools, were the smallest monetary denomination in parts of Africa, India, and the Far East.

Over time, these monies were replaced by coins and for now – it seems coins are here to stay!

Read more about money in “4 Ways Money Moves” here on pendantandring.com.

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