How to do the dice total prediction

A spectator stacks three dice into a tower while you look away. You glance at the top, then announce the total of the five faces nobody can see. It works because opposite faces on a standard die add up to seven, so the hidden faces always total 21 minus the top number. It needs no gimmick and works with borrowed dice.

What does the audience see?

Someone rolls three dice and stacks them into a tower however they like. You glance at the tower for a second, or don’t touch it at all, and write a number on a pad. Then they take the tower apart and add up every face that was hidden: the bottom of each die and the faces that were pressed together. The total matches your number.

Why does it work?

On a standard six-sided die, opposite faces always add up to seven: 1 is opposite 6, 2 is opposite 5, and 3 is opposite 4. A stack of three dice has three top-and-bottom pairs, so all six of those faces together add up to 3 × 7 = 21. Only one of them, the very top face, is visible. The other five are hidden, so they must add up to 21 minus the top number.

If a 4 is on top, the hidden faces total 17. If a 6 is on top, they total 15. You never need to see anything else.

How do you perform it?

1. Check the dice. Make sure opposite faces add up to seven on each one. Most standard dice follow this rule, but always check.
2. Turn away. Ask a spectator to roll the dice and stack them into a tower in any order, turning each die any way they like.
3. Glance at the top. Turn back and look at the tower as if studying it. All you need is the top face.
4. Subtract from 21 in your head and write the answer on a pad or a card. Put it face down.
5. Explain the challenge. Tell them to take the stack apart and add up every face that was touching another die or the table.
6. Reveal. Have them say the total, then turn over your prediction.

Are there easier versions to start with?

• One die. Someone rolls a die and you name the face on the bottom. It is 7 minus the top. It is a good way to practise, but it is easy to work out, so don’t repeat it often.
• Two dice. Someone rolls two dice and tells you the total on top. The two bottom faces add up to 14 minus that total. You can even announce it with your back turned.

How do you make it stronger?

• Use a cover. Have the tower covered with a cup or a paper tube after you glance at it, so it feels as if you are seeing through it.
• Let them stack it more than once. Ask them to rebuild the tower in a new order. Just glance at the new top face each time.
• Write first, reveal last. A number written before the counting starts feels like a prediction, not a calculation.
• Add a tiny delay. Pause before you write, as if you are concentrating. An instant answer looks like arithmetic.

What are the common mistakes?

• Counting the wrong faces. The top face is not counted. Make it clear that only the hidden faces count.
• Odd dice. Some decorative dice use different layouts. Check before you perform.
• Too many repeats. Twice is plenty. After that, people start looking for the pattern.

Where does it come from?

We haven’t found a reliable earliest source for this stacked-dice trick. It is a favourite in maths classrooms because it rests on a simple fact about how dice are numbered. Dice have a long history in conjuring books too: Wiljalba Frikell’s Magic No Mystery (1876) has a chapter on deceptions with dice, and John Nevil Maskelyne’s Sharps and Flats (1894) covers crooked dice in its exposé of card sharps.

What helps you take it further?

• Magic No Mystery by Wiljalba Frikell, free from our public-domain library. Conjuring tricks with cards, balls and dice, including loaded dice, the doctor dice-box and spring tables.
• Sharps and Flats by John Nevil Maskelyne, also free. An exposé of marked cards, stacked decks, holdouts and crooked dice.
• Mental Dice by Tony Anverdi. You hand out three dice, each a different colour, and with your back turned you know which number has been chosen on each one. The set includes a tutorial with seven routines.

For more mind-reading ideas, see our age cards trick and the easy mentalism collection.

Frequently asked questions