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.
✦ Arithmetic → graduate level
Learn math,
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.
2,815 lessons · 87 subjects · a two-minute check finds your starting point
Interactive · Calculus
Feel the slope
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.
How it works
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.
✓
One connected map
From arithmetic to graduate-level proofs.
2,815 lessons across 87 subjects, every skill wired to the ones beneath it. Start anywhere. The map shows what's next.
Your turn
A real Erudia problem.
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.
87
subjects
2,815
interactive lessons
FSRS
retention engine
$0
to start
Pricing
Free to start. Upgrade for the rest.
1,673 of the 2,815 lessons are free, with no plan to charge for them, real analysis and topology included. Premium adds the graduate tier and the contest track.
Free
$0 · no card
- ✓ 1,673 of the 2,815 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
- ✓ 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