Heads or Tails: Which Side Is Which?
Heads is the obverse of a coin, usually the side with a portrait or national emblem; tails is the reverse, usually the side showing the coin's value.
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Heads = obverse, tails = reverse (US Mint)
Heads is the obverse, the front of the coin, and tails is the reverse. The US Mint uses exactly these terms in its glossary: the obverse is heads and the reverse is tails. On most coins the obverse carries a portrait, a head of state or a national emblem, which is where the name heads comes from. The reverse usually shows the value or a separate design. When people argue about which side is which, the simple rule is that heads is the side with the face or the emblem, and tails is the other one. If you are still unsure, agree on it before you flip.
Coins without a face: euro, Indian rupee
On coins without a portrait, heads is simply the side people agree to call heads. Euro coins have one side showing the value that looks the same everywhere and one national side with a design chosen by each country; the national side is often treated as heads. Indian rupee coins carry the national emblem on one side and the value on the other, and the emblem side is commonly called head. These are habits, not official rules. If a coin leaves any room for doubt, settle which side counts as heads before the toss. For a fair flip, the label matters far less than agreeing on it in advance.
What "heads or tails" is called around the world
Almost every language has its own name for heads or tails, and many of them describe what used to be stamped on local coins. The Romans said navia aut caput, ship or head. In medieval England the game was called cross and pile, with pile meaning the reverse. Both names point at the pictures on the coins of the day, and today's heads works the same way, since it names the side with the portrait. Other languages tell similar stories, often naming a ruler, an emblem, a number or a word stamped on the metal. It is a nice reminder that the same simple game has been played with very different coins for a very long time.
How to label a coin flip for a decision
To label a coin flip, assign one option to heads and the other to tails before you toss, and say it out loud. A common pattern is heads for yes and tails for no, or heads for the first option someone named. For two people, each takes a side. If the decision matters, write the labels down so nobody remembers them differently afterwards. In the Yes or No mode on FlipACoin, heads means yes and tails means no by default, and you can type your own labels, such as pizza and tacos. Decision Mode goes further: enter two options or 2 to 8 names and the coin picks, with each result saved to your Decision Log.
FAQ
Is heads or tails more likely?
Neither. In the largest coin-flip experiment to date, with 350,757 hand flips, heads came up 50.0% of the time (95% interval 49.8% to 50.2%), so there was no heads-or-tails bias. The starting side was what mattered: coins landed the same way up they started 50.8% of the time. If nobody sees which side starts up, heads and tails are equally likely.
Which side of a coin is heads?
Heads is the obverse, the front of the coin, which usually shows a portrait, a head of state or a national emblem. Tails is the reverse, which usually shows the value or another design. The US Mint uses exactly these definitions. On coins without a portrait, the side with the country's name or coat of arms is normally treated as heads.