A standard 2x4 LEGO brick has 8 studs.
The “2x4” name describes the brick’s stud layout: two studs across its width and four along its length. Multiplying those dimensions gives eight studs on the top surface. The familiar brick is one of the foundational pieces of the LEGO building system and is often used as the reference shape for explaining LEGO dimensions.
The brick’s proportions are more than a labeling convention. LEGO’s standard grid uses an approximately 8-millimetre pitch between stud centers, allowing bricks of different sizes to connect predictably. A 2x4 brick is therefore about four stud pitches long and two wide, with small allowances for manufacturing tolerances and clearance.
People sometimes confuse studs with the hollow tubes inside the brick. The eight visible studs provide the top connection points, while the internal tubes grip the studs of bricks beneath them. That tube-and-stud arrangement gives modern LEGO bricks their characteristic clutch power and makes the pieces detachable but stable.
The 2x4 brick’s current form dates from 1958, when LEGO patented the modern interlocking design.