How to Solve a Sudoku: Easy Tips & Tricks for Beginners (2025)

Co-authored byPhil Yuand Raven Minyard, BA

Last Updated: December 30, 2024Fact Checked

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Solving a Sudoku: Quick Tips

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   Sudoku is played on a 9x9 grid of squares. A sudoku grid consists of a square grid of 9 large squares, often called blocks. Within each of those blocks will be 9 smaller squares. Some of those squares will be filled with numbers from 1 to 9. Easier puzzles will have more numbers filled in, while more difficult puzzles will have fewer squares filled.^[1]

   • The larger squares are often outlined with a darker line, while the smaller squares have a thinner line. Additionally, sometimes the larger squares will be colored in a checkerboard pattern.
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   Fill the remaining numbers in, making sure they don’t repeat. Each row, column, and block should contain all of the numbers from 1 to 9. That means that within a row, column, or block, a number cannot repeat. Your job is to figure out where each number goes to complete the puzzle.^[2]

   • For example, if a block (large square) already has the number “2” in it, you know it can’t include another “2” anywhere in the square.
   • Similarly, if a column already has a “3,” it can’t have another “3,” even if it’s in a different block.
   • It’s better to use a pencil rather than a pen when solving sudoku. This way, you can erase any mistakes you make and keep your board clean. Remember to write lightly so you can erase better.

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   Look for a single empty cell in a block, column, or row. Examine each large block to see if it has a single square open. Or, run your finger down each row and column to see if they have one empty, as well. These single empty squares are called “naked singles.” They’re easy to fill in because you just have to figure out which number is missing from 1 to 9.^[3]

   • For example, if a block has the numbers 1-3 and 5-9, you know it’s missing the number “4,” which you can fill in.
   • Or, if a column has numbers 1-7 and 9, you know it’s missing the number “8.”
   • This is one of the easiest strategies to use, especially when just starting the puzzle.
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   Scan rows or columns to fill in blocks. Look at a row of 3 blocks and check for a number that’s repeated 2 times in different blocks. Run your fingers along the rows (or columns) that contain that number. The third block must contain the same number, but it can’t be in either of the rows you’re tracing; it must be in the third row. Sometimes, 2 other numbers will be in that row, so you can easily fill in the number you’re scanning.^[4]

   • For example, if “8” is repeated in 2 blocks, look for that number in the third block. Run your finger down the rows with each “8,” as you know the “8” can’t be in either of those rows in the third block.
   • Once you get the hang of scanning across just rows or columns, add the other direction as well.
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   Work in groups of numbers. That is, if you see that you have a lot of one number on the board, it can help to start trying to fill in the rest of that number. For example, say you have a large number of 5s on the board. Use your scanning techniques to fill in as many 5s as you can. This still requires you to examine blocks, rows, and columns to make sure they don’t repeat.^[5]

   • Another option is to include 3 blocks in a row or column in your analysis. Pick 1 number, and see if you can place it across all 3 squares. For instance, take the number "6." See which rows and columns already have 6s, and use that to scan across to the 3 blocks you're looking at. Based on that information and what you have in the squares, try to place as many of the 6s as you can.

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1. 1

   Write down all “candidates” for a square. A candidate is any number that could belong in a certain square. Pencil in all possible entries for each square. Then, check to see if any squares contain only one possible answer. This is a “forced” entry that you can fill in.^[6]

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   Look for “naked pairs.” A naked pair (sometimes called a conjugate pair) is a set of two candidates that could go in two different squares within a block, row, or column. Because you know these numbers must go in one of these squares, eliminate them as candidates in other squares in that block, column, or row.^[7]

   • For example, let’s say you’ve marked all the candidates within a block and you notice the numbers “2” and “8” are the only two candidates that could go in two different squares. These are your naked pairs, so they cannot go in any other square within the block except the two you’ve marked.
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   Eliminate squares using hidden pairs. Hidden pairs are similar to naked pairs, in that they are two numbers that can only go in two cells within a block, row, or column. However, these cells also contain at least one other candidate, which is what makes them “hidden.” Carefully examine the candidates in each of your squares to find two that contain the same two numbers.^[8]

   • For example, let’s say one cell within a block contains the candidates 1, 4, and 7. Another cell contains the numbers 1, 8, and 7. Because they both contain 1 and 7, this is your hidden pair. Eliminate the numbers 1 and 7 from all other cells within the block.
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   Try the X-wing technique on difficult puzzles. An X-wing is an advanced technique used to remove candidates in difficult puzzles. First, look for a row that contains the same candidate in two different spots. Then, find a parallel row that mirrors it and contains the same candidates in the same spots. This allows you to remove those candidates from the columns that contain those cells.^[9]

   • For example, let’s say the first row of the grid contains a 4 as a candidate in the 2nd and 5th squares. The third row of the grid also contains a 4 in the 2nd and 5th squares. This allows you to erase the 4 as a candidate in all other squares in the 2nd and 5th columns, because it must go in either the first or third row.

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   Avoid guessing. If you’ve narrowed a cell down to one or two candidates, you may be tempted to pick one at random. This may result in getting a few more “answers,” but at some point, you’ll likely realize the puzzle is now impossible to solve—often toward the end of the game. To avoid putting in a lot of hard work for nothing, make sure you’re confident about each choice you make.^[10]

   • If you’re stumped by a certain cell, it’s okay to come back to it later. There may be an easier solution somewhere else in the puzzle.
   • Recheck the puzzle often. As you fill in numbers, you may be able to figure out the answers to spaces you had to leave blank before.
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   Retrace your steps. It’s a good idea to do sudoku puzzles in pencil because, odds are, you’ll need to do some erasing at some point. If you realize you made a mistake, try to retrace the last few steps you made. Pay attention to each number to try to determine which one is incorrect. If you can’t find the mistake, it may be easier to start from scratch.^[11]

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   Take a break. If you can’t figure out what to do next, set the puzzle down and take a break. Take some deep breaths or go for a short walk. If you’re frustrated, it will be harder to find the patterns you’re looking for, so return to the puzzle once your brain has had time to relax. You may be able to figure out some answers you couldn’t see earlier.

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   Keep practicing. Sudoku is a game of pattern recognition, which is a skill learned over time. It’s okay to make mistakes, especially if you’re just learning how to play. If you get stuck, don’t get discouraged. Keep trying different puzzles and different techniques until you get the hang of it. Even practicing as little as 5 minutes a day can help!^[12]

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1. Sudoku is based on patterns, not math. While patterns are technically a part of math, solving a sudoku puzzle does not use math as we typically think of it (like adding and subtracting). The use of numbers can be intimidating, but they could actually be replaced with other symbols, like letters or shapes. The game would still be played the same way.^[13]

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