What is the base SI unit for mass?

The base SI unit for mass is the kilogram. In the International System of Units (SI), the kilogram is defined as the mass of a specific prototype kept at the International Bureau of Weights and Measures. It serves as the fundamental standard for mass measurement and underlies most scientific and engineering calculations involving mass. This unit is widely used across various fields due to its fundamental nature in the SI system, making it essential for standardized measurements and comparisons.

While the gram is a commonly used unit for mass, it is technically a derived unit based on the kilogram since there are 1,000 grams in a kilogram. The pound and ounce are units of mass in the imperial system and are not recognized as base SI units, thus placing them outside the context of the standard international definition.