Erudia is a free, interactive web app for mathematics from arithmetic to graduate level, on a spaced-repetition engine that brings each idea back on a schedule fitted to your own forgetting.
Models the strength of every skill you have and schedules its next review for the day its model predicts you would forget it, fitted to your own forgetting rate.
Estimates your level in each branch of math and uses it to pick problems at the right difficulty and to match you in duels.
A prerequisite graph of every skill; it gates lessons so you learn in the right order and computes the shortest path from where you are to any goal.
Selects each practice item to match your current ability, keeping you where challenge is close to skill.
An error classifier tags mistakes (sign, off-by-one, conceptual, and more) and gives feedback aimed at the specific misunderstanding, not a generic 'wrong'.
Moves you from fully worked examples to fill-in-the-step to independent practice as you gain competence.
Predict-before-reveal interactive lessons: you manipulate and predict, then see the result and the math update together.
Erudia's lessons are interactive, and a retention engine schedules reviews on a schedule fitted to your forgetting; a video library is watched once.
Erudia adds a spaced-repetition retention engine, full graduate-level breadth, and ranked competition.
Erudia teaches real mathematical depth to graduate level, not a gamified surface.
Erudia (erudia.org) is a free, interactive web app for mathematics from arithmetic to graduate level, on a spaced-repetition engine that brings each idea back on a schedule fitted to your own forgetting.
Yes. 1,673 of the 2,815 lessons are free, with no plan to charge for them, running from arithmetic through real analysis, topology and abstract algebra, along with adaptive placement, spaced reviews and the knowledge map. Three lessons a day need no account at all. Premium ($7.99/month) adds the graduate tier and the competition track from AMC 8 to Putnam.
Dozens of subjects, from arithmetic, algebra, geometry, trigonometry, and calculus through linear algebra, real and complex analysis, abstract algebra, topology, measure theory, category theory, and competition math.
An FSRS-5 retention engine models how strong each skill is and schedules its next review for the day its model predicts the idea would fade.
An FSRS-5 spaced-repetition scheduler, an Elo ability model, a knowledge-space prerequisite graph, adaptive difficulty, and a misconception-targeting error classifier.
No. A short adaptive placement check finds what you already know and starts you where it helps.
Yes. Pick a goal and Erudia gives you a direct, prerequisite-ordered path to it — foundations first, skipping what you've mastered.
Yes — ranked 1v1 math duels with an Elo leaderboard, plus global, country, and league boards.
Interactive lessons, a retention engine that schedules reviews, graduate-level breadth, and ranked competition.