How to Solve 4x4 Centres: From Bars to the Last Two

How are 4x4 centres different from 3x3?

Each face of a 4x4 has four centre pieces, so the whole cube has 24 of them (Wikipedia). None of them is fixed: they move freely from face to face. That means you have to gather the four pieces of each colour yourself, and put the six centres in the right order yourself too.

In this guide, two centre pieces of the same colour sitting side by side are called a bar, the same word J Perm uses (J Perm). Two bars next to each other make a finished centre.

How to read the pictures. Each picture shows two cubes: before and after the moves. Only the centre pieces are coloured. Edges and corners are grey because you don't need to worry about them yet. You can only see the top, front and right faces.

The colour order of the six centres

A 3x3 has fixed centres, so the order can never be wrong. On a 4x4 you can finish all six centres and still have them in the wrong places, and only find out when you reach the last layer. Get the order fixed in your head before you start:

• White is opposite yellow, green is opposite blue, red is opposite orange.
• With white on top and green in front, red is on the right.
• J Perm has a handy way to remember it: hold white on the left, then go from the bottom up over the front, top and back faces, and you meet blue, orange, green, red in that order (BOGR for short, then it repeats).

According to Ruwix, some brands change the colours or where they go on their cubes (Ruwix). If your cube is different, look at a corner piece: its three stickers tell you which three colours sit next to each other and in which direction. J Perm and Ruwix both suggest this trick.

Step 1: The first centre (white)

J Perm and Ruwix both start with the white centre, then the yellow centre on the opposite face. At this point there is nothing to protect, so you can turn freely.

Hold the cube with the face where you want white on top. Find two white pieces and turn the layers until they sit side by side as a bar. Make one more bar, then put the two bars together.

1. You start with (input)
3. After the formula

Joining two bars. In the picture, one white bar is in the left column of the top face, and the other stands upright in the right column of the front face. One Rw brings the right column of the front face up to the top, and the white centre is done. If the bar on the top face is in the right column, turn U first to move it to the left column, otherwise Rw will push it to the back.

1. You start with (input)
3. After the formula

Adding the last piece. The top face already has three white pieces, with the gap in the far left corner. The missing white piece is in the bottom row, right column of the front face. Do Rw U Rw': Rw lifts the white piece up to the top, U turns it into the left column next to the other white pieces, and Rw' puts the right column back. This is the sequence Ruwix uses to add pieces to a centre one at a time.

Step 2: The second centre (yellow, opposite white)

Flip the cube so the white centre is on the bottom face, and the top face is where yellow goes. From now on there is a new rule: every Rw must be undone with an Rw'. A lone Rw pulls the right column of the white centre off the bottom face. A pair of Rw ... Rw' takes that column away and then brings it straight back.

1. You start with (input)
3. After the formula

Adding a whole bar. In the picture, the top face has a yellow bar in the right column, and the front face has a yellow bar in the right column too. Do Rw U2 Rw': Rw lifts the front bar up, U2 moves it to the left column, and Rw' brings the old yellow bar back to the right column. The yellow centre is done, and the white centre underneath is still in one piece.

1. You start with (input)
3. After the formula

Adding one piece. Same as the last piece of the white centre: the gap is in the far left corner of the top face, the yellow piece is in the bottom row, right column of the front face, then do Rw U Rw'. If the yellow piece is somewhere else on the front face, turn F (or F2, F') to bring it to the bottom row, right column. F doesn't touch the white or yellow centres.

Step 3: The four middle centres

Hold the cube with the white centre on the left face and yellow on the right face, and keep holding it this way until the end. The other four centres are on the top, front, bottom and back faces. The moves Rw, U and F never touch the white and yellow centres, so they are all you need.

1. You start with (input)
3. After the formula

The third centre. Any colour works, but keep the BOGR order from above in mind. J Perm's way: make a bar, stand it upright, make a second bar of the same colour, then join them. In the picture, the front face has a green bar in the left column, and the top face has a green bar in the right column. One Rw' brings that bar down onto the front face. For the third centre you are allowed to do Rw on its own, because there is no middle centre yet that it could break.

The fourth centre. Put it on the top face, right next to the centre you just made. From now on, just like step 2, every Rw needs a matching Rw' so you don't break the centre on the front face. J Perm suggests placing both bars of the same colour on the same side before joining them. The pictures in the next part use exactly these sequences.

Step 4: The last two centres

Two centres are left, on the top and front faces. In the pictures below, the top face is the red centre, the front face is the green centre, and the other four centres are done. Your colours might be different, but the moves are exactly the same. Find the picture that looks most like your cube and follow it.

Two upright bars

1. You start with (input)
3. After the formula

Each face has one red bar and one green bar. Turn U so the green bar on the top face is in the left column. Turn F so the red bar on the front face is in the right column. Do Rw U2 Rw': the two bars swap places, and both centres are done.

One bar lying flat

1. You start with (input)
3. After the formula

If the bar on the top face is lying flat, turn U once to stand it upright, then do the same as the case above. In the picture, the green bar is in the row nearest you, and U moves it to the left column.

1. You start with (input)
3. After the formula

If the bar on the front face is lying flat, turn F to stand it upright. In the picture, the red bar is in the top row of the front face, and F stands it up in the right column.

Three of one colour, one odd piece

1. You start with (input)
3. After the formula

The top face has three red pieces, with the odd green piece in the far left corner. The front face has three green pieces, with the odd red piece in the bottom row, right column. Do Rw U Rw', just like adding the last piece of the white centre.

1. You start with (input)
3. After the formula

If the red piece on the front face is in the top row, right column, then the green piece on the top face needs to be in the near left corner, as in the picture. Do Rw U' Rw'. Turn U first to bring the odd piece on the top face to that corner.

Two diagonal pieces

1. You start with (input)
3. After the formula

The top face has two red pieces diagonal from each other and two green pieces diagonal from each other. There is no bar to join, so you need two rounds. With the front face as in the picture (red bar in the right column), do Rw U Rw' U2 Rw U Rw'. The first round makes a bar, the second one finishes it.

1. You start with (input)
3. After the formula

If the diagonal pieces are on the front face and the top face has two upright bars (red bar in the right column), do Rw U Rw' F2 Rw U Rw'. The middle move is F2 instead of U2, because this time the face that needs turning is the front.

If your cube doesn't match any picture yet, turn U or F and compare again. These two moves only turn the centre of that face, and don't break any other centre.

Put the colours in the wrong order? Here's how to fix it

Sometimes you only notice two centres are in the wrong places after all six are done, or even after the edges are paired. You don't need to start over. J Perm gives two sequences that swap two whole centres. They only use two-layer turns and outer-layer turns, so they don't split any edge pair, but they do mix up where the edges and corners are. So fix it before you start solving it like a 3x3.

1. You start with (input)
3. After the formula

Swap the top centre with the front centre: Rw' F2 Rw2 U2 Rw'. In the picture, the green centre is wrongly on the top face, and the white centre is wrongly on the front face.

1. You start with (input)
3. After the formula

Swap the top centre with the bottom centre: Rw2 U2 D2 Rw2. In the picture, the yellow centre is on the top face. After the sequence, it goes to the bottom face and white comes up to the top.

Tips for faster centres

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3. After the formula

• Do white, then yellow straight away. Once the two opposite centres are done early, the other four only need Rw, U and F.
• Look ahead to the next centre. While you work on white, keep an eye on where the yellow pieces are.
• Join whole bars when you can. One Rw U2 Rw' puts two pieces into the centre, twice as fast as adding them one at a time.
• Check the colour order right after the centres. If you spot it here, it's an easy fix. If you spot it at the last layer, you have to solve the 3x3 part again.

Video

Want to see it in motion? The short video below from the linh HB Vlogs channel on YouTube (in Vietnamese) shows more of what this guide covers. The video belongs to that channel and is embedded straight from YouTube.

Sources

• How To Solve The 4x4 Rubik's Cube – J Perm
• 4x4x4 Rubik's Cube (Rubik's Revenge) – Ruwix
• Rubik's Revenge – Wikipedia