See it first
Each lesson is built around something you drag, sweep, or adjust — you watch a concept move before you're asked to use it.
Learn math,
and keep it for good.
Short, visual lessons. Then the engine re-asks you what its model predicts you're about to forget, on the day it predicts. Months later, it's still there.
3,163 lessons · 98 subjects · a two-minute check finds your starting point
Drag the dot along the curve. The line shows how steep the hill is right there. Find the flat top.
↗
Drag toward the peak.
Nice. Do a real one →
You learned it. Then weeks passed, nothing brought it back, and it faded. That's normal. Timed review is the fix: five minutes today instead of relearning a chapter next month.
Every session does three things.
Reading about an idea is forgettable. Working it yourself, then being brought back to it on time, is what makes it stick.
Practice with feedback that explains
Miss a question and it shows the exact slip: a sign error, an off-by-one. Then that skill comes back later, to be sure it stuck.
✗ sign error
✓ now it sticks
Reviews that return on time
The FSRS engine tracks when each skill is about to fade and re-asks it on that day. Your review time goes where it's actually needed.
✓
From arithmetic to graduate-level proofs.
3,163 lessons across 98 subjects, every skill wired to the ones beneath it. Start anywhere. The map shows what's next.
A real Erudia problem.
No formula to recall.
This is how a lesson feels. You look for the pattern, answer, and the feedback tells you why it works. Give it a shot.
98
subjects
3,163
interactive lessons
FSRS
retention engine
$0
to start
Free to start. Upgrade for the rest.
1,902 of the 3,163 lessons are free, with no plan to charge for them, real analysis and topology included. Premium adds the graduate tier, the contest track and Python in depth.
Free
$0 · no card
- ✓ 1,902 of the 3,163 lessons, arithmetic through real analysis
- ✓ Spaced reviews + progress map
- ✓ Adaptive placement
- ✓ Three lessons a day with no account at all
Premium
$7.99/month
- ✓ The graduate tier, measure theory to category theory
- ✓ Competition prep, AMC 8 to Putnam
- ✓ Python in depth: classes and the data model
- ✓ Olympiad problems with worked solutions
- ✓ A public ★ PRO leaderboard badge
Schools & organizations
Let's talk
- ✓ Erudia for a whole class or school
- ✓ A teacher view of student progress, built with you
- ✓ Lessons shaped to your curriculum
- ✓ One email, answered by the person who builds Erudia