What is the maximum number of discs you can flip in Reversi?
The answer is 19. A live board shows the move, a table proves the limit, and a short method counts flips for any move.
The most opponent discs you can flip in one move on a standard 8×8 Reversi or Othello board is 19. The position below does it, and the table after it shows why no move can flip more.
The 19-disc position
In the position below, Black plays d4. Every line leading away from d4 starts with one or more white discs and ends at a black disc, so all eight directions trap something at once. The position is built to show the geometry. You won't meet it in a normal game.
Why the maximum is 19
A capturing line needs three things: the disc you place, at least one unbroken run of opponent discs, and one of your own discs at the far end. That far disc anchors the line and doesn't flip. So in each direction, the most you can flip is the number of squares to the edge minus one.
From d4 the counts are:
| Direction from d4 | Squares to the edge | Most flips |
|---|---|---|
| Up | 3 | 2 |
| Down | 4 | 3 |
| Left | 3 | 2 |
| Right | 4 | 3 |
| Up-left | 3 | 2 |
| Up-right | 3 | 2 |
| Down-left | 3 | 2 |
| Down-right | 4 | 3 |
| Total | 27 | 19 |
Playing on d5, e4 or e5 gives the same total by symmetry. No other square has longer lines in all eight directions, so 19 is the upper limit.
Does the placed disc count?
No. Flipped discs are opponent discs that change colour. In the example, Black places one new disc and flips 19 white ones, so 20 discs on the board turn black, but only 19 were flipped.
Flipping in all eight directions
Reversi checks every row, column and diagonal from the square you play. Each line with an unbroken run of opponent discs followed by one of yours flips in the same move. You can't choose to leave a trapped line as it is. The World Othello Federation rules require every outflanked disc to flip, and the 19-disc maximum comes from applying that rule to the longest lines an 8×8 board allows.
How to count flips
The same method works for a puzzle solver or a game engine. For each of the eight directions:
- Start one square away from the move.
- Count consecutive opponent discs.
- If the run ends at one of your own discs, keep that count.
- If it reaches an empty square or the edge first, that direction flips nothing.
- Add up the counts from all eight directions.
Our Reversi engine works this way. It scans each direction on its own, collects the discs trapped between the new disc and an anchor of the same colour, and adds them up.
Is the biggest flip the best move?
Usually not. Beginners often chase the move that flips the most discs right now, but strong players care more about mobility, corners, stable discs and which moves they leave the opponent. A quiet move that flips one disc can be far stronger than one that flips ten. The beginner strategy guide and common mistakes explain why.
What is the most discs Black can flip in one Reversi move?
19 opponent discs. The same limit applies to White.
Is the maximum the same in Othello?
Yes. It comes from the geometry of the 8×8 board and the outflanking rule that modern Othello and online Reversi share.
Can a corner move flip 19 discs?
No. A corner has only three directions into the board, so it can't trap eight lines at once. The 19-disc maximum needs one of the centre squares d4, d5, e4 or e5.
Is Reversi the same as Othello for this puzzle?
Yes. With the modern 8×8 outflanking rules the flip count is the same. For the history and naming, see Reversi vs Othello.
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