The Rydberg constant is known to seven parts in a trillion.

The Rydberg constant can also be expressed as the following equations.

The Rydberg constant is the most well-determined physical constant, with a relative experimental uncertainty of less than 7 parts in 10.

The Rydberg constant is written:

Instead, the Rydberg constant is inferred from measurements of atomic transition frequencies in three different atoms (hydrogen, deuterium, and antiprotonic helium).

The physical constant known as the Rydberg constant is named after him, as is the Rydberg unit.

Since the Bohr model is not perfectly accurate, due to fine structure, hyperfine splitting, and other such effects, the Rydberg constant cannot be directly measured at very high accuracy from the atomic transition frequencies of hydrogen alone.