How Sticky Schedules Your Reviews So You Never Forget

Ever wonder what happens behind the screen when you tap Easy, Medium, or Hard on a flashcard? It is not random, and it is not a simple timer. Sticky uses a battle-tested algorithm called SM-2 to calculate exactly when each card should reappear so you review at the moment that matters most: right before you would have forgotten.

This post walks you through how the system works, why it is effective, and what each tap actually does to your study schedule.

The Problem: When Should You Study?

The biggest challenge in learning is not understanding new material. It is retaining it. Research on the forgetting curve shows that without review, you lose 50 to 70 percent of new information within 24 hours.

But reviewing too soon wastes time. If you re-study a fact five minutes after learning it, you get almost no benefit because the memory is still fresh and the review adds nothing.

The sweet spot is reviewing just before the memory fades. That is where Sticky's scheduling engine comes in.

Inside the SM-2 Algorithm

SM-2 (SuperMemo 2) is a spaced repetition scheduling algorithm created by Polish researcher Piotr Wozniak in 1987. It calculates optimal review intervals for each flashcard based on three variables: ease factor, repetition count, and current interval. Every time a user rates a card, the algorithm updates all three values and sets a new review date.

Sticky's review scheduler is built on SM-2. It is one of the most widely used spaced repetition algorithms in the world, trusted by millions of learners and refined over decades.

SM-2 tracks three values for every single card in your collection:

• Ease Factor (EF): a number (starting at 2.5) that reflects how natural the card feels to you. Higher means the card is easy for you; lower means you find it difficult.
• Repetition Count: how many times in a row you have successfully recalled the card.
• Interval: the number of days until the card should appear again.

Every time you rate a card, all three values update simultaneously. The result is a personalised schedule that is different for every card and adapts to your performance over time.

What Happens When You Tap Easy, Medium, or Hard

Each response teaches Sticky something different about your relationship with that specific card. Here is what changes under the hood.

Hard: "I struggled"

When you tap Hard, Sticky interprets this as a failure or near-failure. The card resets:

• The repetition count drops back to zero
• The interval resets to 1 day, so you will see this card again tomorrow
• The ease factor decreases, making future intervals grow more slowly for this card

This is not a punishment. It is the algorithm recognising that this particular card needs more reinforcement. You will see it frequently until you prove mastery.

Medium: "I got it, but it took effort"

Medium signals a successful recall that required some thought. This is the most common response and the engine of gradual progress:

• The repetition count increases by one
• The interval extends based on the current ease factor (if you were at 6 days, you might jump to 15)
• The ease factor stays roughly the same, shifting only slightly

Over time, cards you consistently rate as Medium graduate from short intervals (1 day, 6 days) to long ones (weeks, then months).

Easy: "I knew it instantly"

Tapping Easy tells Sticky that retrieval was effortless. The algorithm responds aggressively:

• The repetition count increases
• The interval jumps significantly, so the card might not appear again for weeks or months
• The ease factor rises, which compounds over time into increasingly long intervals

Cards rated Easy quickly move to the background of your study routine. You will still see them periodically for maintenance, but they will not dominate your daily sessions.

A Card's Journey: From New to Mastered

Here is what a typical card lifecycle looks like inside Sticky:

1. Day 0: You create the card (or AI generates it from your notes). It enters the "new" queue.
2. First review: You see the card for the first time and rate it. If you tap Medium, the interval becomes 1 day.
3. Day 1: The card appears again. You rate Medium again. The interval jumps to 6 days.
4. Day 7: Third review. You rate Easy this time. The interval jumps to about 15 days, and the ease factor ticks upward.
5. Day 22: Fourth review. Another Easy. The interval extends to around 38 days.
6. Day 60: Fifth review. The card is becoming deeply embedded. The interval stretches to over two months.

Within five reviews, a card can go from brand new to appearing once every few months. That is the power of exponential interval growth: each successful recall makes the next interval longer.

If at any point you tap Hard, the card resets to a short interval and works its way back up. The system is self-correcting.

Unified Review: One Session, All Your Decks

One feature that makes Sticky particularly efficient is unified review. Instead of opening each deck individually and reviewing cards one subject at a time, Sticky pulls every due card across all your decks into a single review session.

This means:

• No guessing what to study. Open the app, tap Review, and Sticky shows you exactly what needs attention today.
• Interleaving built in. You might see a Spanish vocabulary card followed by an AP Biology card followed by a history date. Research on interleaving shows that mixing subjects during review strengthens discrimination and improves retention.
• Nothing falls through the cracks. Even if you have ten decks with thousands of cards, the algorithm ensures every card appears at its optimal time. You never have to manually check which deck needs attention.

The "Review Due" section on Sticky's home screen shows your total count of due cards. When it hits zero, you are done for the day.

Why SM-2 Beats Fixed Schedules

You could try to manage your own review schedule: study everything on Day 1, Day 3, Day 7, Day 14, Day 30. Some people use this approach with spreadsheets or calendar reminders, similar to a manual Leitner system.

The problem is that a fixed schedule treats every card identically. In reality:

• Some cards are easy for you and do not need frequent review
• Some cards are harder and need shorter intervals
• Your performance on a specific card changes over time

SM-2 solves this by making each card's schedule individually adaptive. Two cards in the same deck can have completely different intervals based on your history with each one. A vocabulary word you find intuitive might be scheduled for 45 days out, while a chemistry formula you keep confusing might appear every 3 days, and those schedules adjust automatically as you improve.

The Result: Shorter Sessions, Better Retention

The net effect of SM-2 scheduling is that your daily review sessions are as short as they can possibly be while still maintaining high retention. The algorithm surfaces only what you are about to forget and leaves everything else alone.

As your card collection grows, the review load does not scale linearly. Most mature cards are on long intervals (weeks or months), so even with thousands of cards, your daily review count stays manageable, typically 5 to 15 minutes.

This is fundamentally different from re-reading notes or cramming before a test. With Sticky, every minute of study time is targeted at the cards that need it most, when they need it most.

Getting Started with Scheduled Reviews

Ready to let the algorithm do the scheduling for you? Here is how to start:

1. Create or import your cards. Use Sticky's AI card creator to snap a photo of your notes, or paste text and let AI generate cards for you.
2. Review daily. Open the app and tap Review. The algorithm does the rest. Just rate each card honestly.
3. Trust the system. If a card feels too easy, rate it Easy and it will appear less often. If you are struggling, rate it Hard and it will come back sooner. The algorithm adapts to you.
4. Stay consistent. The biggest factor in spaced repetition success is showing up every day. Daily streaks and quiz mode help you build the habit.

The science is clear: spaced repetition with adaptive scheduling is the most efficient way to move information from short-term to long-term memory. Sticky handles the scheduling. You just need to show up.