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Understand it in class. Still know it next week.

Add your notes right after class. A 5-minute check shows what stuck, then Lemma reteaches, refreshes or drills you and brings it back before you forget. The same notes become an interactive study guide.

Add your first class freeTry a real study guide

30 credits freeno card neededbuilt by a math tutor

Two things from one upload

Add today's class once. Lemma uses the same notes for both, and keeps everything for that class together on one class page.

Remember it

A quick check right after class, the right next step for your score, then free reviews before it fades.

An example class: the first check, then the free reviews.
  • Class check: 6–8 questions on today's notes, about 5 minutes, checked as you go.
  • Your score suggests what's next: a Reteach lesson, a Quick refresh or more practice (Easier, Like class, Harder or Exam-level).
  • The check comes back free on days 1, 3 and 7, and every score adds to the class's memory line.
  • An email when a review is due, if you turn reminders on.

Class check from 5 credits. Follow-ups 5 to 20 credits. Reviews free.

More about class checks

Study guide

Your notes rebuilt as one interactive page, to study from tonight and again before the test.

An example from a study guide. The real one is live further down this page.
  • Worked examples you reveal one step at a time.
  • Graphs and diagrams you can move.
  • Practice that checks your answers, with hints.
  • A cheat sheet and the mistakes that cost points.

Quick study guide from 15 credits. Full study guide from 45 credits.

Try a real study guide

One upload, right after class

  1. Step 1: Add your notes after class

    Paste typed notes, or add photos of handwritten pages, PDFs or a worksheet. Pick a class check (from 5 credits), a study guide (from 15 credits) or both. You see the exact price before you click.

  2. Step 2: Take the 5-minute check

    6–8 questions on what you just learned, checked as you go. Your score shows what stuck while it's still fresh.

  3. Step 3: Fix the gaps and keep it

    Lemma suggests a Reteach lesson, a Quick refresh or more practice, then brings the check back free on days 1, 3 and 7. Your study guide from the same notes is on the class page too.

Why it comes back on days 1, 3 and 7

If you don't use what you learned, most of it fades within days. That's how memory works for everyone, not a sign you're bad at math.

Pulling an idea back out of your memory, like answering a quick question on it, and doing it again a few days apart, are among the best-studied ways to remember. Each review is short, and each one tends to make the next drop smaller.

what you rememberclassday 1day 3day 7day 10
With reviews on days 1, 3 and 7Without reviewsAn illustration of the idea, not measured data.

Messy notes in. A real study guide out.

A page of Calculus I notes, question marks and all, and the study guide made from them, running live in the same locked-down viewer your pages use. Try a practice problem: nothing you do here is saved.

The notes

Calc 1 — Derivative rulesCh 3.1–3.4 · my notes

Power rule: d/dx [xn] = n xn-1

ex: d/dx [x5] = 5x4

ex: d/dx [1/x2] = -2x-3 = -2/x3

Product rule: (fg)' = f'g + fg'

ex: d/dx [x2 sin x] = 2x cos x <- check this one??

Quotient rule: (f/g)' = (f'g - fg') / g2

"low d-high minus high d-low, over low squared"

Chain rule: d/dx f(g(x)) = f'(g(x)) · g'(x)

ex: d/dx [(3x + 1)4] = 12(3x + 1)3

Prof said: always simplify!!

Quiz Friday — tangent lines: y - f(a) = f'(a)(x - a)

Handwritten notes: Power rule: d/dx [x^n] = n x^(n-1). ex: d/dx [x^5] = 5x^4. ex: d/dx [1/x^2] = -2x^(-3) = -2/x^3. Product rule: (fg)' = f'g + fg'. ex: d/dx [x^2 sin x] = 2x cos x <- check this one??. Quotient rule: (f/g)' = (f'g - fg') / g^2. "low d-high minus high d-low, over low squared". Chain rule: d/dx f(g(x)) = f'(g(x)) · g'(x). ex: d/dx [(3x + 1)^4] = 12(3x + 1)^3. Prof said: always simplify!!. Quiz Friday — tangent lines: y - f(a) = f'(a)(x - a)

It even answers the “check this one??”: that product-rule example was wrong, and the study guide shows the fix.

The study guide

Live demoCalculus I: derivative rules and tangent lines
Live demo

Calculus I: derivative rules and tangent lines

A real lesson, running on this page in the same sandboxed viewer your lessons use. Nothing you do here is saved. In your own library, your progress is.

Everything a good tutor would hand you

Every study guide is one interactive page, made from your notes and built to be studied, not just read.

1. Progress you can see. A progress bar with a check for every finished section, and points (XP) for correct answers that count toward your streak.

2. Built from your notes. Examples from your own notes are labeled "From your notes" and use your teacher's notation.

3. Step-by-step worked examples. Solutions appear one step at a time behind "Show next step", so you try first and only peek when you're stuck.

4. Interactive visuals. Sliders, graphs and diagrams you can move, for the ideas that click once you see them change.

5. Practice with hints and instant checking. A hint first, then the steps, then the answer.

6. A concept check. Quick multiple-choice questions with an explanation for every option.

7. Cheat sheet + mistakes that cost points. The key formulas and steps on one page, plus the common slip-ups to watch for on the test.

8. A mastery summary. At the end: your score, the XP you earned and exactly what to review, with links back to it.

Works for any math class

For class checks and study guides alike: high school or college, plus the math inside other subjects.

  • Pre-algebra
  • Algebra 1 & 2
  • Geometry
  • Trigonometry
  • Precalculus
  • Calculus I, II & III
  • AP Calculus AB & BC
  • Statistics
  • AP Statistics
  • Linear algebra
  • Differential equations
  • Discrete math & proofs
  • Physics & engineering math
  • Chemistry math
  • Economics math
  • Computer science math

Studying for AP Calculus or the SAT?

Ready-made courses, separate from your own classes: every unit as interactive lessons, with practice tests. One payment each.

See the courses

Built by a math tutor

I'm a math major and a math tutor. Almost every week, a student brings me a page of notes they copied down in class, and they can't study from it. The steps that made sense on the board don't make sense at home.

So I built Lemma to do what I do in a tutoring session: start with why an idea works, walk through the problems from your own notes one step at a time, then give you practice that tells you right away whether you've got it.

Accuracy comes first. A study guide with a wrong answer is worse than no study guide, so every lesson is made with the instructions I'd give myself: work every problem completely, double-check every step, and use your notation. If you ever spot a mistake, every lesson has a "Report a mistake" button, and those reports come straight to me.

Thomas, founder of Lemma

For parents

The short version of what matters when your teen signs up. The FAQ, pricing and privacy pages have the details.

FAQPrivacy policyTerms

  • Notes are deleted

    Uploaded notes are deleted once the pages made from them are ready; only a short text summary stays with the class. Everything is private to the student's account.

  • 13 and older

    Accounts are for students who are 13 or older.

  • Credits come back

    If a lesson can't be made, the credits go back to the account automatically.

  • Cancel any time

    The weekly, monthly and yearly plans can be cancelled any time from the account page.

  • Report a mistake

    Every lesson has a "Report a mistake" button that sends the problem to us to check.

Free to start. A plan when you need more.

Every new account gets 30 credits, enough for a class check, a Quick refresh and a Quick study guide. After that, $15 a month buys 180 credits, about $1.25 per Quick study guide. Reviews are always free, and you see every price before you click.

Free to start

Available now

$0

30 credits when you sign up

Monthly plan

Available now

$15/month

180 credits every month

About $1.25 per Quick study guide

Also weekly ($5) or yearly ($150, 17% off)

Top-up packs

Available now

$5and up

Extra credits when you need them

See pricing details

Questions students ask

Read all questions

What's a class check?

A short quiz on one class: add your notes right after class, and Lemma makes 6–8 questions on just what you learned. It takes about 5 minutes, and every answer is checked as you go, so you see what stuck while it's still fresh.

It costs 5 credits from a page of notes. Each extra PDF page, photo or 2,000 typed characters: +1 credit. You see the exact price before you click, and you can make a study guide from the same notes at the same time.

Are the reviews free? When are they?

Yes, reviews are free. 1, 3 and 7 days after your first check, the class's check comes back as a review, on the class page and at the top of your library. You already paid for it, so there's nothing to pay.

You answer the same questions again with your old answers cleared, and each score adds a point to the class's memory line, so you can watch it stick. Missed one? Take the next one: it counts for the ones you skipped.

Want new questions instead? A new check made from the class costs 5 credits.

What happens to the notes I upload?

Your notes are private to your account. We use them only to make your lessons: your class check, your study guide and their follow-ups.

Once everything you picked for an upload is made (the class check, the study guide or both), the files you uploaded are deleted. What was made from them stays in your library until you delete it.

To make refreshers, practice and reviews later, Lemma keeps a short text summary of each class (never the photos or files). Deleting the class deletes it.

You can delete any class from its class page. "Delete my account and data" on the Account page removes everything: your notes, classes, lessons, progress and credit history.

Lessons are written by an AI model (Claude, made by Anthropic) following teaching instructions written by a math tutor. To make your lesson, your notes are sent to Anthropic for that one job. The way we use Anthropic's service, your notes aren't used to train AI models.

Read the privacy policy

Are the lessons accurate?

Accuracy is the whole point. Every lesson is made with instructions to work each problem completely and double-check every step before writing it. If your notes contain a mistake, the lesson points it out gently and shows the fix.

Still, no study guide is perfect. If something looks off, check it against your textbook or ask your teacher, and use the "Report a mistake" button on the lesson so we can fix it.

Had class today? Add your notes while it's fresh.

Your first class is free: 30 credits, enough for a class check, a Quick refresh and a Quick study guide. No card needed.

Add your first class free