How to do the heads or tails prediction

Count the heads on the table and note whether the number is odd or even. Turn your back. Every time the spectator flips a coin and says “Turn”, switch your odd or even word. When they cover one coin with their hand, turn round and count the heads you can see. If that count is the same odd or even as your word, the hidden coin is tails. If it is different, the hidden coin is heads. It works every time, with any number of coins.

What does the audience see?

A handful of coins lie on the table, some heads up and some tails up. You turn your back. The spectator turns over any coins they like, as many times as they like, saying “Turn” each time. Then they cover any one coin with their hand. You turn round, glance at the table, and tell them whether the coin under their hand is heads or tails. You can repeat it straight away and still be right.

What do you need?

• Some coins. Any number works; somewhere between eight and fifteen is easy to count at a glance. They can be borrowed and do not need to match.
• A table. Somewhere the coins can lie flat while you have your back turned.

How do you do it, step by step?

1. Spill the coins. Have someone spread the coins on the table in a mix of heads and tails.
2. Count the heads. Casually count how many coins show heads. You only need to know whether that number is odd or even.
3. Turn your back. Explain the rules: they can turn over any coin, as often as they like, but each time they turn one they must say “Turn”.
4. Keep the code. Each time you hear “Turn”, switch your word in your head: odd becomes even, even becomes odd. Remember the last word you land on.
5. The cover. When they are finished, ask them to cover any one coin with their hand.
6. Count again. Turn round and count the heads you can see.
7. The reveal. If the visible heads are the same odd or even as your word, the covered coin is tails. If they differ, the covered coin is heads. Make it look like a feeling, not a sum.

Why does it work?

The trick uses parity, the idea of odd and even. Every time one coin is turned, the number of heads goes up or down by exactly one, so it switches between odd and even. By switching your word on each “Turn”, you always know whether the total number of heads is odd or even, even though you never see a single flip. When one coin is hidden, comparing the visible heads with that total tells you whether the missing coin is a head. The same principle is used in computing, where a parity check can show that a single bit, or a single card or coin, has been flipped.

How can you present it better?

• Go further away. Leave the room or put on a blindfold. All you need to hear is each “Turn”.
• Try the silent version. Ask them to turn coins two at a time without saying anything. Turning two coins never changes whether the number of heads is odd or even, so you only need to remember the starting count.
• Count without counting. Glance at the table for a moment and look away before you answer. Practise counting heads in small groups so it is quick and invisible.
• Do it twice, then stop. Two hits prove it was not luck. More than that gives people time to look for a pattern.

What helps you take it further?

• Mathematical Recreations and Essays by W. W. Rouse Ball, free from our public-domain library. Its arithmetical recreations and puzzles make it a favourite source for self-working and number-based effects.
• Modern Coin Manipulation by T. Nelson Downs, also free. His 1900 book on palms, passes, vanishes and the Miser’s Dream, for when you want coin magic with sleight of hand.
• Magic No Mystery, credited to Wiljalba Frikell, free as well. It includes coin tricks, deceptions with dice and a chapter on magic writing.

Next, try the magic number nine trick, the 1089 number trick and the dice total prediction, and browse our easy mentalism and ungimmicked coins.

Frequently asked questions