IconVault's Grade Calculator computes your weighted course grade from your assignments. Add rows with each assignment's score, total points and weight, and it instantly shows your current grade, how many items are counted and whether your weights add up.

It also includes a final exam forecaster: enter the final's weight and your target grade, and it tells you exactly what score you need on the final, flagging when the target is already locked in or mathematically out of reach. It is free with no signup and runs fully in your browser, so your grades stay private. The honest caveat: it uses the simple weighted-average formula, so confirm with your syllabus if your class drops lowest scores or uses a curve.