The SAT reports one total, and that total is simply two section scores added together. Reading and Writing runs from 200 to 800, Math runs from 200 to 800, and the sum falls between 400 and 1600.
Two sections, equal weight
The two sections count the same. This is easy to state and easy to forget in practice, because most students prepare more heavily for the side they are already stronger in.
The arithmetic is unforgiving here. A student with 800 in Math and 550 in Reading and Writing reaches 1350, and no further work on Math can raise it, because 800 is the ceiling. The remaining points exist only on the other side.
No penalty for a wrong answer
Nothing is deducted for an incorrect response. An unanswered question and a wrong one score identically, which means leaving a question blank is never the better option.
The practical rule follows directly: every question receives an answer, even where the answer is a guess made in the final seconds.
How the module structure affects the score
Each section is delivered in two modules, and the difficulty of the second module depends on performance in the first. A student routed to the harder second module is competing for a higher score band.
This is why the number of correct answers alone does not explain a score. Two students can answer the same number correctly and finish with different totals, because they were answering different papers.
What counts as a good score
There is no single answer, and the question is better asked against a destination. Each university publishes the score range of its admitted students, and the target is read from that range rather than from a general figure.
A score that is strong for one institution is below the range at another. This is covered under the entry on target university scores.
How long a score lasts
SAT scores do not expire in the way that some language certificates do, and universities generally accept scores from earlier years of secondary school. What changes is how a very early score is read, which is dealt with under when to start.