How to Memorise Formulas You Keep Forgetting

You write the formula on your hand, on a card, on the back of your exercise book. You recite it before bed. Then the paper asks a question and you cannot tell which of the six formulas you memorised applies to it.

That is not a memory problem, which is why more memorising does not fix it.

Knowing a formula and knowing when to reach for it are two different pieces of knowledge, and examinations test the second one. Almost all wasted formula revision comes from drilling the first and never practising the second.

First, check which ones you are given

Before memorising anything, find out what is printed in the paper.

Many syllabuses include a formula sheet, or state which relationships candidates are expected to know and which are provided. Students routinely spend weeks memorising things that will be handed to them, and then fail to memorise the ones that are not, because they assumed the sheet covered everything.

Get the sheet, print it, and mark it up. Anything on it needs recognition rather than recall. Anything not on it needs to be in your head.

This is one of several reasons to read your syllabus properly rather than working from notes, covered in our guide to reading a syllabus and finding what will actually be examined.

Understand where it comes from

A formula you understand is far harder to forget than one you memorised, and if you do forget it you can rebuild it.

You do not need a full derivation. You need to know what the formula is saying. That speed is distance over time is not an arbitrary arrangement of letters, it is the sentence “how far, divided by how long” written compactly. Once you hear the sentence, rearranging it under pressure stops being a memory task.

For each formula you keep losing, write one line in words explaining what it means. If you cannot, that is the real gap, and it is why the formula will not stay.

Build the card around the situation, not the formula

This single change fixes most of the problem.

The instinctive card has the formula name on the front and the formula on the back. It tests recall of something you were already looking at, and it does not resemble the exam at all.

Weak card	Strong card
Front: the formula’s name Back: the formula	Front: a situation Back: which formula, and why that one
Tests: can I recite it	Tests: can I recognise when it applies
Exam asks this: rarely	Exam asks this: constantly

So the front of a good card reads like a question stem. “You are given the mass and the volume and asked for the density.” “A vehicle accelerates uniformly and you know the initial speed, the acceleration and the time.” The back names the formula and, crucially, says what in the question told you it was that one.

Build both kinds if you like, but the recognition cards are where the marks live. Review them on a schedule using the method in our twelve week revision plan.

Learn the trigger words

Questions signal which relationship they want, and the signals repeat across years.

Go through past papers and, for each question, write down the phrase that told you which formula to use. Then group them. You will find a small number of recurring signals doing most of the work: uniformly, at constant, per unit, given that it starts from rest, in terms of.

That list is worth more than any formula sheet, because it is the missing translation layer between the question and the maths, and nobody teaches it explicitly.

Practise mixed, never in blocks

Doing twenty questions from the chapter on one topic teaches you almost nothing about selection, because you already know which formula applies before you read the question.

Shuffle instead. Take questions from several topics and do them mixed, so that each one requires you to work out what kind of problem it is before solving it. Accuracy will drop, which feels like going backwards and is not, and the skill that improves is the one being examined.

This is the same reason blocking subjects fails generally, and it applies with particular force here.

Use units as a check

A practical safeguard that costs seconds and catches real errors.

If you are unsure whether you have arranged a formula correctly, check whether the units work out. A calculation producing metres when the answer should be in seconds has gone wrong somewhere, and you know that before the examiner does.

Units also help you reconstruct a half remembered formula. If you know density is measured in kilograms per cubic metre, the arrangement of mass and volume is no longer something to recall.

Where mnemonics help and where they do not

They are useful for arbitrary ordering, such as a sequence with no underlying logic to hold onto. They are actively harmful when used instead of understanding.

The failure mode is specific and common: you remember the mnemonic, cannot remember what the letters stood for, and now have a string of initials and no formula. Or you remember it correctly and still cannot tell which question it applies to, which was the real problem.

Use them as a top layer over understanding, never as a substitute for it. If a mnemonic is doing all the work, you have not learned the thing.

Write them out, do not read them

Reading a list of formulas produces familiarity, which feels like knowledge and is not.

Close the book and write down every formula for a topic from memory. Then check. The ones missing are your actual revision list, and it is almost always shorter than the full list, which means you have been spending time on things you already knew.

Do this weekly rather than daily. The gap is what makes it a test rather than a copying exercise.

The exam day version

If a formula genuinely goes, do not sit there trying to summon it.

Write down what you do know about the situation, including the quantities you have been given and their units. Very often that produces the relationship, or produces enough working to earn method marks even if you never reach the final answer. A blank scores nothing and partial working frequently scores something.

Then move on and come back. Retrieval usually returns once the pressure is off that specific question.

Build one sheet of your own

Not a copy of the textbook list. A single page, in your handwriting, containing only what you personally keep losing.

The making is most of the value. Deciding what belongs on it forces you to work out what you actually know, and the page ends up short, which is itself reassuring when the full list feels overwhelming.

Organise it by situation rather than by chapter. Group everything you might use for one kind of problem together, so the page mirrors how you will search your memory in the exam rather than how the book was structured.

Rewrite it from memory every couple of weeks rather than reading it. The rewriting is the revision, and each version gets shorter as things become secure.

It differs by subject

In mathematics, most of the difficulty is rearrangement and selection rather than recall, so practise mixed problems rather than lists.

In physics, units and the meaning of each symbol carry you a long way, and a formula whose quantities you can describe in words is one you can reconstruct.

In chemistry, the recurring difficulty is usually the relationship between moles, mass and volume, and securing that one properly removes a surprising share of the problem.

Questions students ask

How many formulas should I know?

Fewer than you think. Work from the syllabus and the formula sheet rather than from a textbook’s full list, because textbooks include material beyond what is examinable and you have no way of telling which is which.

Is it cheating to derive one instead of memorising it?

Not at all, and it is more robust. The only cost is time, so use derivation as your safety net for things you occasionally lose rather than as your primary method for everything.

I know the formula but always rearrange it wrongly.

That is an algebra problem rather than a formula problem, and it will surface across every subject that uses mathematics. Practise rearranging directly, as its own exercise. It is usually a foundation gap carried forward, and fixing it pays back across everything.

Should I write formulas down as soon as the paper starts?

Check whether your examination permits it before relying on it, since rules vary. Where it is allowed, dumping a few onto the paper in the first minute can relieve some pressure. It is not a substitute for knowing which one applies.

Try this now

Take five formulas you keep forgetting. For each, write one line in words saying what it means, and one card whose front describes a situation rather than naming the formula.

Then do six mixed past paper questions and notice how often the difficulty was choosing rather than calculating. For most students it is nearly always choosing.

More method in Study Skills.