Sudoku 6×6 – Easy

Sudoku 6x6

Sudoku 6x6 is a variant of classic Sudoku with a 6x6 grid. The puzzle consists of 6 rows and 6 columns. Some cells are already given, the remaining cells are empty. The goal is to fill all empty cells so that each region is complete and free of conflicts. The numbers 1 to 6 are used.

Sudoku 6x6 is not a calculation puzzle. The entered symbols are not added, multiplied, or otherwise calculated together. They serve only as distinguishable symbols. What matters is where a number can be placed and where it is excluded by row, column, or region.

Basic Rules

• The playing field consists of 6 rows and 6 columns.
• Exactly 6 different numbers are used: 1 to 6.
• The playing field is additionally divided into regions. In this variant, they are regions of 2 rows x 3 columns.
• Exactly one number is entered into each empty cell.
• Each row must contain each number exactly once.
• Each column must contain each number exactly once.
• Each region must contain each number exactly once.
• Pre-filled entries may not be changed.
• The puzzle is solved when all cells are filled and no row, column, or region contains duplicates.
• A well-constructed Sudoku has exactly one solution. Therefore, one should not guess, but only place logically justified entries.

Strategies for Solving

The most important mindset is elimination. An entry is only certain if all other possibilities are excluded by the rules or if a particular number can only be in one place within a region.

1. Start with almost complete regions

The simplest start is rows, columns, or regions where many numbers are already filled in. The more entries, the fewer options remain open.

In the first row, only the number 6 is missing from the six possible numbers. Therefore, 6 must be in the last cell of the first row.

This conclusion is clear because only one number is missing in this region. Such obvious gaps are especially good starting points.

2. Single candidate: when a cell has only one possibility

A cell always belongs to three regions: its row, its column, and its region. All numbers already present in these regions are excluded for this cell.

The following complete grid considers the top-left cell. In the first row, the entries 1, 3, 6 are initially missing. The first column excludes all these possibilities except 1. Therefore, only 1 remains for the top-left cell.

So, the top-left entry is certain. It is not guessed, but deduced because all other candidates are excluded by the column, and the entry also fits the region.

3. Hidden single: when a number only fits in one spot

Sometimes, an empty cell has several possible candidates. Still, a specific number can only be in one position within a row, column, or region. Then this entry is also certain.

In the next example, we look at the top-left region and search for the entry 5. The existing 5s outside this region block certain rows and columns. Consequently, only the top-left cell remains in the top-left region.

Since 5 can only be in the top-left region at the top-left cell, 5 must be entered there.

The difference from a single candidate is important: not necessarily the cell itself had only one possibility. Instead, the number being searched had only one possible position in the considered region.

4. Track a number systematically across the whole grid

A very typical Sudoku technique is to systematically follow a particular number. For example, choose 6 and check in which rows, columns, and regions this entry already appears. Each existing position blocks further positions in the same row, column, and region.

5. Note and update candidates

If no immediately certain entries are visible, it pays to note candidates. Candidates are all numbers still allowed in a cell based on the current state. After each new entry, update these candidates in the affected row, column, and region.

Important: A candidate is not a guess. It merely indicates that an entry is not yet excluded. Only when there is only one candidate left or a candidate fits in only one place within a region, can it be safely entered.

Candidate pairs come into play especially when single candidates are no longer enough. If two cells in the same row, column, or region have exactly the same two candidates, these candidates are bound there and can be removed from other cells in the same region.

6. Check all three conditions before every entry

An entry is only correct if it fits the row, column, and region simultaneously. A common mistake is to check only one row and overlook that the same number already appears in the column or region.

• Does the number already appear in the row?
• Does the number already appear in the column?
• Does the number already appear in the region?
• Is the entry truly unique, or are there other possible positions?

Only when this check is thoroughly completed should a cell be filled.

Typical solving sequence

A Sudoku is not solved rigidly from left to right. It is more sensible to repeatedly look for the strongest hints: nearly full rows, nearly full columns, nearly full regions, and entries that already occur frequently.

1. Check first rows, columns, and regions with many clues.
2. Look for areas where only few numbers are missing.
3. Check individual cells by combining row, column, and region.
4. Look for single candidates: cells with only one possible number.
5. Look for hidden single candidates: numbers that can only go in one place in a region.
6. Systematically track individual numbers across the grid.
7. Note candidates when no immediately certain entries are visible.
8. Update candidates after each certain entry.
9. Use region-row and region-column logic to exclude more candidates.
10. Regularly verify that no row, column, or region contains duplicates.

Common mistakes

• Guess too early instead of drawing secure conclusions.
• Only check rows and columns but forget regions.
• Note candidates but do not update them after new entries.
• Overlook hidden single candidates by only checking individual cells instead of entire regions.

Tips for beginners

• First get used to the numbers used: 1 to 6.
• Start with regions where many entries are already filled.
• Always check row, column, and region for every entry.
• Look for safe exclusions, not just cells you can fill.
• Note candidates once you can no longer proceed immediately.
• Remove candidates only when the exclusion is justified by a rule.
• Ask yourself with every entry: Why must exactly this number go here?
• Periodically change perspective: from rows to columns, from columns to regions, and from regions to individual numbers.
• Keep the grid clear. For larger Sudokus, unclear notes can lead to mistakes quickly.
• Work slowly and carefully rather than quickly and erratically.

Sudoku 6x6 follows the same logical principles as classic Sudoku but adapts them to a 6x6 grid. By consistently combining rows, columns, and regions, you can also solve this variant step by step without guessing.