Ah, dice stacking. The popular pastime of stacking dice in a cup... Wait, what? You've never heard of it?

Dice stacking is the art of using a cup to stack dice. There is no trick, but a scientific principle, inertia. The dice are first picked up by the cup, and because of the motion of the cup resist movement like a bucket of water swung around. As a result, the dice stack inside the cup and slide around as if they were a single mass.

Step 1: What You Need

To start dice stacking, you'll need:

Dice
A cup

That's about it. More specifically, you'll need

Heavy casino dice / standard dice / rounded-edges dice
Speed stacks cup / yahtzee cup / short plastic cup

In order from recommended to needed.

Step 2: How This Works

When you pick up the first dice, you swing the cup back and forth, alternating similar angles. By holding the cup still on only two positions, the dice slides around the sides of the cup. The uniform motion swings the dice equally and the dice are stacked inside the cup. When you stop the dice on the table, the dice swing to the opposite side of the cup and stop, resting on the weight of the force created by sliding the cup.

See below for 2D picture example

Step 3: Picking Up the Dice

Picking up the dice may seem trivial, but it's the part most people get wrong.

First, approach the dice at a 45 degree angle. Sharply switch directions as you strike the dice, as it rises to the top, hold the cup at an almost 90 degree angle. Repeat this process until all the desired dice are in the cup. Its similar to cradling a lacrosse ball. For reference, look at my video on the introduction.

Note: Practice this away from windows until you master it. I am not responsible for broken windows or black eyes.

Step 4: Stopping the Dice

This is the hard part. If you passed step 3, nicely done! you got farther than most people ever will.

Now, to stack the dice, you finish your current swing, and then slide the cup along the ground as if it were another swing. You almost fool the dice into thinking you just swung the cup again. Then you stop short.

Its very difficult to explain. The most important thing to get out of this is that you need to stop short. It takes practice. A LOT of practice. If you need help, watch videos on youtube. They are a big help.

Step 5: Variations

Dice stacking can be very broad. There are many variations of the basic stack. These are only limited by your imagination, so I won't list to many here. Common variations are:

Point stops - Stopping the dice on small areas, usually Rubik's Cubes or other stacks.

Downstacks - Stacking dice, then removing dice with the cup one by one.

All-in-one - Grabbing all the dice in one swing, than stacking them.

One person that can really push the limits of dice stacking is Dennis. He is the pioneer of dice stacking, and he is just amazing.

Step 6: Perform!

This trick is very impressive, and if you attempt this in public: Expect people to want to examine the dice or cup. People generally won't believe you if you say there is no trick, so go ahead and taunt them. Claim supernatural powers or give them headaches by letting them try to pick up one dice, only for them to miserably fail. It's fun!

Good luck!