Mental Math Daily is a free browser-based tool for practicing the calculations that come up constantly in exams, interviews and everyday life: multiplication tables, squares, cubes, powers and quick arithmetic. Each session is timed and scored, your accuracy by topic is tracked automatically, and anything you get wrong is queued into a review list until you can answer it correctly twice in a row.
It works fully offline once installed, keeps a daily streak to encourage short regular practice over long infrequent sessions, and stores all of your progress locally in your own browser — no account, no sign-up, no data leaves your device.