Use this GCSE physics equations guide as a practical formula sheet for revision, homework and exam practice. It groups the most commonly assessed equations by topic, shows the SI units to use, explains how to rearrange formulas safely and provides worked examples you can repeat with your own values. Always check your exam board specification and the formula sheet provided for your assessment, because the exact list and presentation can vary.
Overview
Memorising a GCSE physics equation is only the first step. In an exam, you also need to identify the quantities, convert them into compatible units, choose the correct rearrangement and give a sensible final answer. A reliable routine is:
- Write the equation before substituting numbers.
- List the values you know, including their units.
- Convert units where necessary, usually to SI units.
- Rearrange the equation if the unknown is not already the subject.
- Substitute carefully and check the unit and size of the answer.
Keep a separate version of your GCSE physics formula sheet for each course you study. AQA, Edexcel and OCR specifications overlap considerably, but not every equation is assessed or supplied in exactly the same way. The GCSE Physics Revision Checklist by Topic and Exam Board can help you compare your revision against the correct specification.
Common GCSE physics equations by topic
- Motion: speed = distance ÷ time; acceleration = change in velocity ÷ time.
- Forces: resultant force = mass × acceleration; weight = mass × gravitational field strength; momentum = mass × velocity.
- Energy: kinetic energy = 0.5 × mass × speed²; gravitational potential energy = mass × gravitational field strength × height; work done = force × distance; power = energy transferred ÷ time.
- Thermal physics: energy transferred = mass × specific heat capacity × temperature change; energy transferred = mass × specific latent heat.
- Density and pressure: density = mass ÷ volume; pressure = force ÷ area; pressure in a liquid = height × density × gravitational field strength.
- Waves: wave speed = frequency × wavelength; magnification = image height ÷ object height.
- Electricity: charge flow = current × time; potential difference = current × resistance; power = current × potential difference; energy transferred = power × time; efficiency = useful output ÷ total input × 100.
- Elasticity: elastic potential energy = 0.5 × spring constant × extension².
- Transformers, where included: primary potential difference ÷ secondary potential difference = number of primary turns ÷ number of secondary turns.
Some equations are presented using symbols rather than words. For example, density is written as ρ = m ÷ V, potential difference as V = I × R, and wave speed as v = f × λ. Learn what each symbol represents rather than memorising letters in isolation.
How to estimate and calculate an answer
Physics calculations become more manageable when you treat them as a repeatable process. Begin by deciding what the question is asking for. If it asks for speed, write speed = distance ÷ time. If it asks for distance, rearrange to distance = speed × time. Writing the rearranged form prevents you from placing values in the wrong part of the equation.
For equations involving multiplication, divide both sides by the factor you want to remove. For example, from weight = mass × gravitational field strength, mass = weight ÷ gravitational field strength. For a squared quantity, take the square root only after isolating it. From kinetic energy = 0.5 × mass × speed², speed² = kinetic energy ÷ (0.5 × mass), so speed is the square root of that result.
Use estimation as a checking tool, not as a replacement for the calculation. If a 2 kg object moves at 3 m/s, its kinetic energy should be close to 9 J because 0.5 × 2 × 3² = 9. A result of 90 J or 0.09 J would suggest a calculator, substitution or powers-of-ten error.
Show your working even when the calculation looks simple. A correct equation and substitution can protect method marks if your final arithmetic is wrong. For guidance on how these marks are awarded, read Physics Mark Schemes Explained.
Inputs and assumptions: units, prefixes and data
Most GCSE physics equations work best when values are converted to SI units first. Use metres for distance, seconds for time, kilograms for mass, cubic metres for volume, newtons for force, joules for energy, amperes for current and volts for potential difference. A value given in centimetres, grams or minutes may need converting before substitution.
Watch prefixes particularly carefully. kilo means 1,000, milli means one thousandth, micro means one millionth and nano means one billionth. Thus 250 mA is 0.250 A, while 3.0 kJ is 3,000 J. For a volume, remember that converting a length unit and converting a volume unit are not the same operation. The SI Units and Prefixes Revision Guide is useful for building this habit.
Use the value of gravitational field strength printed in the question unless instructed otherwise. Do not silently replace it with a different value. Similarly, do not assume that every question requires a formula from memory: some exams provide equations, and the supplied formula sheet should take priority over an older revision poster.
Round only at the end of a multi-stage calculation. Keep extra digits in your calculator, then give the final answer to the number of significant figures or decimal places requested. If no instruction is given, a sensible level of precision is usually better than a long string of calculator digits.
Worked examples
Example 1: kinetic energy
A cyclist and bicycle have a combined mass of 80 kg and travel at 5 m/s. Calculate the kinetic energy.
Start with kinetic energy = 0.5 × mass × speed².
Kinetic energy = 0.5 × 80 × 5² = 1,000 J.
The speed is squared, so entering 5 rather than 25 would produce an incorrect result. The unit is joules because kinetic energy is a form of energy.
Example 2: electrical power
A device operates at 12 V and draws a current of 2.5 A. Calculate its power.
Power = current × potential difference.
Power = 2.5 × 12 = 30 W.
If the question then asks for energy transferred in 4 minutes, convert the time to 240 seconds and use energy transferred = power × time: 30 × 240 = 7,200 J.
Example 3: rearranging density
A metal sample has a mass of 540 g and a volume of 200 cm³. Calculate its density in g/cm³.
Density = mass ÷ volume = 540 ÷ 200 = 2.7 g/cm³.
Because both inputs use compatible centimetre-based units, no conversion is needed for this answer. If the question requested kg/m³, convert the quantities before calculating or convert the final value using the appropriate volume relationship.
When to recalculate and update your formula sheet
Revisit this resource at the start of each revision cycle, after your teacher confirms your exam board and tier, and whenever your specification or supplied formula sheet changes. You should also recalculate your understanding after a topic test exposes a repeated error, such as confusing mass with weight or minutes with seconds.
For effective GCSE physics revision, do not read the list passively. Cover one side of a formula card, recall the equation and units, then answer a short topic question without looking. After marking it, record the exact error: wrong equation, unit conversion, rearrangement, arithmetic or interpretation. Use that error log to choose your next practice set. Once your basics are secure, work through GCSE Physics Equations: Formula Sheet with Worked Examples and then test yourself with past-paper questions.
Before an exam, complete this final check:
- Confirm the specification and whether you are studying separate or combined science.
- Practise rearranging equations without relying on a triangle diagram.
- Convert units before pressing the calculator buttons.
- Write units beside intermediate values and the final answer.
- Check powers, square roots and significant figures.
- Compare your working with the mark scheme, not just the final number.
A formula sheet is most useful when it becomes a decision-making tool: identify the quantity, choose the relationship, standardise the inputs, calculate, and check whether the result makes physical sense.
