How to read a Stockfish position evaluation
What +0.5, −2.0 and a mate score mean, why the number keeps moving, and when the chances matter more than the pawns.
The sign tells you whose side it is
A positive evaluation means white is better, a negative one means black is. A small plus is not a promise of a win: with accurate play one side is only a little more comfortable. A number near zero is not a simple draw either — the board can still hold hard decisions and good practical chances.
The number is measured loosely in pawns
An evaluation of +1 is usually read as an advantage of about one pawn, but it is not a literal count of material. It also covers piece activity, king safety, the pawn structure and tactical chances. Two positions with the same number can differ a lot in difficulty and in how easily a human finds good moves.
The evaluation does not grade your move
The number describes the position after the chosen continuation, not the beauty of one decision. To judge your own move, compare the evaluation before and after it from the same side. The change between neighbouring positions tells you more than the absolute value: it shows the moment where the chances moved.
Why the result keeps being refined
The analyzer checks the most promising replies first and then searches deeper. If the position hides a tactic, the evaluation can move noticeably after a longer check. So do not draw a conclusion from the first number: wait for a stable result and see whether the idea survives in several continuations.
What a mate score means
A score like «mate in 4» means that against the best defence one side can finish the game in that many of its own moves. If the defence plays differently, the mate may become shorter or longer. In practice it matters more to see the first threat and the defence against it than to memorise the whole sequence.
Follow a continuation you can understand
If the best move looks strange, walk a few replies on the board and ask which threat it prevents or creates. Compare it with the natural human move and find the first difference. A short idea you can check is worth more than a long line you cannot hold in your head.