Reversi puzzle answer
What Is the Maximum Number of Discs You Can Flip in Reversi?
The maximum is 19 opponent discs in one move on a standard 8×8 Reversi or Othello board. Here is the puzzle solution, the geometry behind 19, and a simple way to count flips correctly.
Direct answer
19 discs
A single placed disc can outflank opponent discs in all eight directions at once. From one of the four central squares, the longest possible legal lines add up to 19 flipped discs.
The 19-disc Reversi puzzle setup
In the illustrative position below, Black plays on D4. Every neighboring line begins with one or more White discs and ends at a Black anchor, so all eight directions are valid captures.
A B C D E F G H
1 ● · · ● · · ● ·
2 · ○ · ○ · ○ · ·
3 · · ○ ○ ○ · · ·
4 ● ○ ○ ★ ○ ○ ○ ●
5 · · ○ ○ ○ · · ·
6 · ○ · ○ · ○ · ·
7 ● · · ○ · · ○ ·
8 · · · ● · · · ●
This diagram is designed to show the legal outflanking geometry clearly; it is not meant to represent a typical position you would see in normal play.
Why the maximum is exactly 19
The key is that a capture line needs three things: the disc you place, at least one continuous opponent disc, and one of your own discs at the far end. The far-end disc is an anchor, so it does not get flipped.
D4 is one of the best squares for maximizing line length because it can reach far toward every edge. Count the available squares in each direction and reserve the final square for the Black anchor:
| Direction from D4 | Squares to edge | Maximum flips |
|---|---|---|
| North | 3 | 2 |
| South | 4 | 3 |
| West | 3 | 2 |
| East | 4 | 3 |
| North-west | 3 | 2 |
| North-east | 3 | 2 |
| South-west | 3 | 2 |
| South-east | 4 | 3 |
| Total | 19 | |
2 + 3 + 2 + 3 + 2 + 2 + 2 + 3 = 19
Moving the target square to D5, E4, or E5 gives the same geometry by symmetry. No other square can provide longer capture rays in all eight directions, so 19 is the upper limit.
Does the disc you place count as one of the 19?
No. “Flipped discs” means opponent discs that change colour. In the maximum example, Black places 1 new disc and flips 19 White discs. That means 20 board discs become Black as a direct result of the move, but only 19 were flipped.
Can one Reversi move flip discs in all 8 directions?
Yes. Reversi checks horizontal, vertical, and diagonal lines from the square you just played. If each valid line contains a continuous run of opponent discs followed by one of your own discs, every valid line flips in the same move.
The official Othello rules also require you to flip all discs outflanked by the move; you cannot choose to keep one valid direction unchanged.
How an algorithm counts flipped discs
The same logic works for a puzzle solver or a Reversi game engine. For each of the eight directions:
- Start one square away from the proposed 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 board edge first, that direction flips zero.
- Add the valid counts from all eight directions.
That is also the pattern used by the PlayFaceToFace Reversi engine: it scans each direction independently, collects the discs bracketed by the newly placed disc and a same-colour anchor, then sums the captured count.
Is flipping the most discs always the best move?
Usually not. Reversi beginners often chase the move that flips the largest number immediately, but strong play is more concerned with mobility, corners, stable discs, and what moves you give the opponent next. A quiet move that flips one disc can be much stronger than a move that flips ten.
If you want to improve beyond the puzzle, read our Reversi beginner strategy guide and common Reversi mistakes.
Frequently asked questions
What is the largest number of discs Black can flip in one Reversi move?
19 opponent discs.
What is the maximum number of discs any player can flip in Othello?
Also 19. The maximum comes from the geometry of the standard 8×8 board and the same outflanking rule used in modern Othello-style play.
Can a corner move flip 19 discs?
No. A corner has only three inward directions, so it cannot create eight capture lines at once. The 19-disc maximum needs a central square such as D4, D5, E4, or E5.
Is Reversi the same as Othello for this puzzle?
For the modern 8×8 outflanking rules used in this puzzle, the flipping calculation is the same. For the historical naming and rule differences, see our Reversi vs Othello comparison.
Try the flipping rules in a real game
Play a few rounds and watch how the same directional scan works on every legal move. The game highlights legal squares and flips captured discs automatically.
Reversi
