Square Nanometer [nm²]
A square nanometer (nm²) is a unit of area equal to a square with sides 1 nanometer long (1 nm = 1 billionth of a meter, or 10⁻⁹ m).
It’s used to measure extremely tiny areas, like the surface of molecules or nanomaterials.
1 nm² = 1 × 10⁻¹⁸ m².
Acre [ac]
An acre (ac) is a unit of area commonly used in the United States and other countries for measuring land. One acre equals 43,560 square feet or about 4,047 square meters.
1 acre ≈ 0.4047 hectares or 0.004047 square kilometers.
Acres are often used to describe the size of farms, plots, and real estate.