Study Tips
Physics: How to Answer Calculation Questions Without Losing Marks
By Daniyal Ahmed · · 7 min read
Quick answer
Most physics marks are lost to process, not physics. Write down what you know with units, select the equation and state it, substitute clearly, then evaluate — showing every step. You earn method marks even when the final number is wrong, but only if the working is visible. Always check units and whether the answer is physically sensible.
Working is worth marks on its own
Physics mark schemes award credit for the method: selecting the correct equation, substituting correctly, rearranging properly. A student who makes an arithmetic slip at the last step but shows clear working keeps most of the marks. A student who writes only a wrong final answer gets nothing.
So never do the calculation in your head or on the calculator alone. The working is not a courtesy to the examiner; it is where a large share of the marks live.
A four-step routine
Write what you are given, with units and symbols. State the equation you will use, in symbols, before substituting. Substitute the numbers clearly. Then evaluate, and state the answer with the correct unit and a sensible number of significant figures.
That routine feels slow for the first few questions and then becomes automatic — and it is remarkably robust under exam pressure, when panic otherwise makes students skip straight to the calculator.
Units catch your own errors
Units are not bureaucracy; they are a free error-checking system. If you are calculating a force and your units come out as kilograms per second, you have made a mistake, and you have caught it before the examiner did.
Convert to SI units at the start rather than mid-calculation — centimetres to metres, grams to kilograms, kilojoules to joules. Mixed units are one of the most common and most avoidable sources of lost marks.
Rearrange before you substitute
Rearranging the equation with symbols first, then putting the numbers in, produces fewer errors than substituting early and then trying to untangle a messy numerical expression. It also makes your working far easier to follow and to credit.
Does the answer make physical sense?
Take five seconds at the end. A car accelerating at 400 metres per second squared, a resistance of 0.0002 ohms in a household circuit, a wavelength longer than the room — these should trigger an internal alarm. Physics is about the real world, and the numbers should look like it.
Students who develop this instinct catch errors that would otherwise cost them entire questions.
'Explain' and 'describe' questions need words, not numbers
Not all physics marks come from calculations. Explanation questions reward a clear chain of reasoning — cause, mechanism, consequence — using correct terminology. Practise writing these out, because they are frequently the questions students revise least and lose most on.
Graphs and practicals
Know how to draw a line of best fit, calculate a gradient properly using a large triangle, and interpret what the gradient and intercept physically represent. Practical-skills questions reward precision about variables, uncertainty and reliability, and they are highly predictable — which makes them reliable marks.
Show your working — the marks are in it
In physics, most marks in a calculation are method marks: writing the correct equation, substituting correctly, rearranging properly. A student who reaches the wrong final number but shows correct method can score most of the marks; a student who writes only an answer and gets it wrong scores nothing.
So always write the equation first, then the substitution, then the answer with units. Even when you can do it in your head, write it down.
Units and significant figures
Unit errors are the most common avoidable loss in physics papers — converting cm to m, minutes to seconds, kilojoules to joules. Convert everything to SI units before you substitute, as a matter of habit, and you eliminate an entire class of mistakes.
Check that your answer is physically sensible, too. A car travelling at 3,000 m/s or a person with a mass of 4 kg should trigger an immediate recheck.
For further reading, BBC Bitesize is a reliable, authoritative source. When you are ready for personal help, explore our physics tutoring or book a free demo session.
Frequently asked questions
Do I get marks if my final answer is wrong?+
Usually yes — physics mark schemes award method marks for correct equation selection, substitution and rearrangement. But only if you have written the working down. An unsupported wrong answer scores zero.
How many significant figures should I use?+
Generally match the least precise value in the question, unless the paper says otherwise. It is a small habit that quietly protects a mark on many questions.
Do I need to memorise all the equations?+
It depends on your board — some provide an equation sheet, some do not. Even where one is provided, knowing the equations well makes you far faster, because you are not hunting through a sheet under time pressure.
Which boards do you cover?+
GCSE, IGCSE, O-Level, A-Level and IB physics across the major boards including AQA, Edexcel, OCR and Cambridge, taught to your specific specification.
What should I do if I can't remember the equation?+
Check whether it is on your formula sheet — many boards provide one, and students routinely forget to use it. If not, try deriving it from a relationship you do remember, and always write down what you know and what you are looking for, as that often reveals the route.
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