How to Get Sub-20 on a Rubik's Cube: A Step-by-Step Plan

What is sub-20, and where do the 20 seconds go?

"Sub-20" means an ao12 under 20 seconds: the average of 12 solves, leaving out the fastest and the slowest. One lucky 19-second solve does not count. How ao5 and ao12 are worked out is explained in How to solve the Rubik's Cube faster.

In his sub-20 guide on the Cubelelo blog, Sarthak Masta splits a 20-second solve like this: about 12 seconds for the cross and F2L, 4 seconds for OLL and 4 seconds for PLL (Cubelelo). These numbers are only a rough guide, but they show one thing: more than half the solve is the first two layers.

So the first job is to find out where you are slow. Time each step on its own a few times: just the cross, then the cross plus F2L, then the whole cube. The step that is furthest from the numbers above is the one to practise first.

F2L: where you save the most time

J Perm writes that F2L is not hard to understand at first, but practising it is where you will spend most of your time (J Perm). The Cubelelo post also calls F2L the part that needs the most work to get to sub-20.

For comparison, the SpeedSolving Wiki says F2L takes about 6.7 moves per pair on average, so about 27 moves for all four pairs (SpeedSolving Wiki). If you often need 10 moves or more for one pair, that is where to cut.

The pictures below hold the white face on the bottom, just like in a real solve.

Turn the whole cube less: insert straight into the back slots

Every time you turn the whole cube (y or y'), your eyes lose track of the pieces for a moment. Cubelelo suggests inserting pairs into the back slots instead of turning the cube twice, and using your left hand too, not just R and U.

The shortest insert is three moves: the corner sits in the top layer, right above its slot, and the edge sits in the top layer on the other side of the cube. For a front slot the edge is at the back; for a back slot the edge is at the front. The same idea works for all four slots, with no cube turns:

Front right slot: R U R'

Back right slot: R' U' R

Front left slot: L' U' L

Back left slot: L U L'

Notice how the four algorithms are linked: the back right slot is the front right slot with every move turned the other way; the back left slot is the front right slot with R swapped for L. Once you see this, you do not have to memorise four separate algorithms. More ways to insert into the back slots are in Advanced F2L tips.

Use an empty slot

When another slot is still unsolved, you can use it as a "spare" spot and insert your pair faster. In the example below, the front right slot needs solving and the back right slot is still empty. The usual way takes 8 moves:

U' R U R' U R U R'

If the back right slot is empty, the same case takes only 5 moves, all R and U:

R' U R2 U R'

The second picture does not colour in the back right slot, because the pieces there get mixed up. That is why this trick only works when that slot is not solved yet. Saving three moves each time may sound small, but across four pairs and hundreds of solves a week, it adds up.

Turn slower so you can look ahead

The SpeedSolving Wiki calls look-ahead the art of seeing what comes next: while you solve one pair, you are already finding the next one (SpeedSolving Wiki). According to Sarthak Masta, many people get stuck at around 22 to 23 seconds because they turn too hard and then pause for a long time between pairs. His advice is to turn more calmly so your eyes can keep up with your hands.

How to practise: solve the whole cube at a speed where your hands never stop, however slow that is. Your times on those solves will be bad, and that is fine. Once you can solve without pausing, speed up a little at a time.

Get full PLL before full OLL

In the last layer, a common question is: should you add more OLL or more PLL first? Sarthak Masta's answer is clear: 2-look PLL is not enough for sub-20, so get all 21 PLL cases; full OLL is not needed yet, you just need to make 2-look OLL really smooth (Cubelelo).

The reason is easy to see: PLL has 21 cases, OLL has 57. And with 2-look PLL, in about 7 out of 10 solves you have to do two PLL algorithms (we counted on the simulator: 208 out of 288 arrangements). Full PLL brings all of them down to one algorithm.

Start with the two J-perms

From 2-look PLL you already know 6 algorithms: T, Y, Ua, Ub, H and Z. That leaves 15 more. A good place to start is Ja and Jb: they are short, easy to spot, and each one comes up about once every 18 solves. If you only know 2-look and you get a J, you have to do two algorithms; we tried every option on the simulator and none of the six 2-look algorithms solves a J in one go.

The two pictures below hold the yellow face on top.

Jb-perm: R U R' F' R U R' U' R' F R2 U' R'

Ja-perm: R' U L' U2 R U' R' U2 R L

How to spot all 21 cases, with their algorithms, is in PLL algorithms.

What order to get the other 15 PLLs in

We counted on the simulator: once the last layer is oriented, there are 288 possible arrangements (counting a top layer that is turned out of line). Most PLLs take up 16 of those, so each one comes up once every 18 solves. The four G-perms together take up 64, about 2 in every 9 solves, so do not leave them until the very end.

The order we suggest, from easiest to hardest:

Take one round, use it in real solves for a few days, then move on to the next. J Perm warns that cramming too many algorithms at once makes you forget them (J Perm).

OLL: 2-look is enough, but it has to be fast

According to Cubelelo, you do not need full OLL to get sub-20. What you do need is to do 2-look OLL without having to think. Look back at 2-look OLL if there is anywhere you still pause.

Once you have full PLL and want to add more, start with short OLLs that you get often. Here are two examples, with the yellow face on top. Each algorithm makes the whole top face yellow in one go instead of two.

OLL 33, the top has 2 yellow edges in a straight line and 2 yellow corners: R U R' U' R' F R F'

OLL 37, the top has 2 yellow edges next to each other and 2 yellow corners: F R' F' R U R U' R'

All 57 cases are in OLL algorithms: all 57 cases.

The cross and 15 seconds of inspection

At a WCA competition you get up to 15 seconds to inspect the cube before you start (WCA Regulations, A3a1). Sarthak Masta suggests using that time to plan the whole cross, and once the cross feels easy, to find the first F2L pair as well. When you are just starting out, you can inspect for longer, then bring it down to 15 seconds bit by bit.

J Perm writes that with plenty of practice the cross can be done in under 5 seconds (J Perm). If your cross still takes longer than that, see How to do the CFOP cross.

Weekly practice plan

This is the plan we suggest if you practise about 30 minutes a day. It does not come from any source, so adjust it to your own slowest step.

Write your ao12s down in a table. Look at them week by week, not day by day: some days being slower than the day before is normal. EasyRubic's 3x3 timer page gives you scrambles and times each solve.

Mistakes that keep you stuck at 22 to 25 seconds

• Going for full OLL too early. 57 algorithms take weeks, while slow F2L is still the biggest problem.
• Turning at full speed every time. Fast hands with eyes that cannot keep up lead to long pauses between pairs.
• Turning the whole cube to insert into a back slot. Every turn is another moment of losing track of the pieces.
• Solving over and over without knowing where you are slow. Time each step on its own now and then.
• Looking at one great solve instead of your average. Only your ao12 tells you whether you are sub-20.

Video

Want to see it in motion? The short video below from the Snake VN cubing channel on YouTube shows more of what this post covers. The video belongs to that channel and is embedded straight from YouTube.

Sources

• How to be Sub-20 in 3x3 (Sarthak Masta, Cubelelo)
• CFOP Method – J Perm
• F2L (SpeedSolving.com Wiki)
• Lookahead (SpeedSolving.com Wiki)
• WCA Regulations (World Cube Association)