North America:
* Letter: 8.5 inches by 11 inches (216 × 279 mm)
* Legal: 8.5 inches by 14 inches (216 × 356 mm)
* A4: 8.27 inches by 11.69 inches (210 × 297 mm) (also commonly used in Canada)
Europe and many other parts of the world:
* A4: 8.27 inches by 11.69 inches (210 × 297 mm)
* A5: 5.83 inches by 8.27 inches (148 × 210 mm)
* B5: 7.17 inches by 10.24 inches (176 × 257 mm)
Asia:
* A4: 8.27 inches by 11.69 inches (210 × 297 mm)
* B5: 7.17 inches by 10.24 inches (176 × 257 mm)
* Japanese B5: 6.93 inches by 9.84 inches (176 × 250 mm)
It's important to note that these are just a few common default paper sizes, and there can be variations or additional standard paper sizes used in specific regions or industries.