Based on the FSRS algorithm
Australia students · Year 11 & Year 12
Remember every formula, and revise none of the ones you already know.
DxByDy turns the formulas in your syllabus into cards, then schedules each one for the day you are about to forget it. Physics, chemistry, biology and maths in a single deck.
Free to download on iOS and Android. No card limits, no subscription.
Your rating sets the next review date. Nothing else to configure.
Three steps, then repetition does the work
A review session is short by design. Most students finish the day’s queue in under ten minutes.
01
Pick your subjects
Choose the courses you are sitting. Every formula on the syllabus arrives as a card, already written and checked.
02
Recall, then rate
Read the prompt, say the formula from memory, reveal it and rate how the recall felt. Four buttons, no marking.
03
Come back when told
Cards you find easy move weeks or months ahead. The shaky ones stay close until they hold.
The scheduler
Memory fades on a curve. Reviews reset it.
Left alone, a formula you learned today is mostly gone within a week. A review just before that point pulls recall back up, and the next fade is slower.
dxbydy uses FSRS, a free open scheduling algorithm, to estimate that fade for each card from your own ratings. It aims to show a card when your chance of recalling it has dropped to about 90%.
Recall over time
Each amber point is a review. Intervals widen because the fade gets slower every time.
Four decks, written for the syllabus
Every card carries the formula, its variables with units, and the conditions under which it applies.
Physics
F = ma
Mechanics, waves, electricity, fields, nuclear. 142 cards.
Chemistry
pV = nRT
Moles, gases, energetics, equilibria, rates. 96 cards.
Biology
M = I / A
Magnification, respiration, genetics, statistics. 61 cards.
Maths
∫ u dv
Algebra, trigonometry, calculus, vectors. 118 cards.
Questions
For students, and for the parents and teachers who ask what this actually does.