The highest break that can be made under normal circumstances is 147.
To achieve that, the player must pot all 15 reds, with the black after
every red, followed by potting the six remaining colours. This "maximum
break" of 147 rarely occurs in match play. The fastest maximum break in a
tournament was achieved during the World Championships on April 21,
1997, by Ronnie O'Sullivan against Mick Price in 5 minutes and 20 seconds.
If an opponent fouls before any balls are potted, and leaves the player a free ball, the player can then nominate a colour and play it as a red ball. Then, black can be nominated as the next colour. This means it is actually possible to score the value of 16 reds and blacks (16 * 8), plus the values of all the colours (27), which equals 155 points scored. Under tournament condition, Jamie Burnett achieved 148 points.
The highest possible score, as distinct from the highest possible break, is unlimited and depends on the value of points scored from the opponent's foul shots when added to the player's own scored points (which may not require the highest break). However, the highest possible score from a single visit clearance is 162 (foul on the black, followed by a free ball treated as a red, as above).
If an opponent fouls before any balls are potted, and leaves the player a free ball, the player can then nominate a colour and play it as a red ball. Then, black can be nominated as the next colour. This means it is actually possible to score the value of 16 reds and blacks (16 * 8), plus the values of all the colours (27), which equals 155 points scored. Under tournament condition, Jamie Burnett achieved 148 points.
The highest possible score, as distinct from the highest possible break, is unlimited and depends on the value of points scored from the opponent's foul shots when added to the player's own scored points (which may not require the highest break). However, the highest possible score from a single visit clearance is 162 (foul on the black, followed by a free ball treated as a red, as above).