How are the seats in the two bodies of legislative branch are divided among the states?

I interpret this question to refer the the US Federal government. If that is incorrect, my answer is wrong.

Each state receives 2 seats in the Senate. That number is fixed in Article 1, Section 3 of the US Constitution.

The House of Representatives is divided proportionately among the states based on population. Every 10 years, a census is conducted and seats are reapportioned based on current population.This is covered in Article 1, Section 2 of the Constitution.

The total number of members of the House is not actually fixed in the Constitution. In the early years of the US, the number of seats was periodically increased as the overall population increased. At some point, it was decided that 435 members was enough and the total number was fixed by law. Every new census results in some states gaining and some states losing seats in the house.

Everyone gets two Senators. Congress is split up by population; each state gets at least 1 and the total must reach 435.

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