IGCSE Physics 0625 equations
There is no equation sheet in the IGCSE Physics exam: you must recall these. This list follows the 2026–2028 syllabus. Equations marked Extended are Supplement content.
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1 Motion, forces and energy
- Speed
- v = s ÷ tv in m/s, s in m, t in s
- Average speed
- average speed = total distance ÷ total timem/s
- Acceleration Extended
- a = Δv ÷ Δta in m/s², Δv in m/s, Δt in s
- Gravitational field strength
- g = W ÷ mg in N/kg, W in N, m in kgOn Earth g = 9.8 N/kg.
- Density
- ρ = m ÷ Vkg/m³ or g/cm³
- Spring constant Extended
- k = F ÷ xk in N/m, F in N, x (extension) in m
- Force, mass and acceleration Extended
- F = maF in N, m in kg, a in m/s²
- Moment of a force
- moment = force × perpendicular distance from the pivotN m
- Momentum Extended
- p = mvkg m/s
- Impulse Extended
- impulse = FΔt = Δ(mv)N s
- Resultant force and momentum Extended
- F = Δp ÷ ΔtN
- Kinetic energy Extended
- Eₖ = ½mv²J
- Change in gravitational potential energy Extended
- ΔEₚ = mgΔhJ
- Work done
- W = Fd = ΔEJ
- Efficiency Extended
- efficiency = (useful energy output ÷ total energy input) × 100%% (or the same with power)
- Power
- P = W ÷ t and P = ΔE ÷ tP in W, E in J, t in s
- Pressure
- p = F ÷ Ap in Pa (N/m²), F in N, A in m²
- Pressure change in a liquid Extended
- Δp = ρgΔhPa
2 Thermal physics
- Gas at constant temperature Extended
- pV = constant (p₁V₁ = p₂V₂)any matching units
- Kelvin temperature
- T (in K) = θ (in °C) + 273K
- Specific heat capacity Extended
- c = ΔE ÷ (mΔθ)J/(kg °C)
3 Waves
- Wave speed
- v = fλv in m/s, f in Hz, λ in m
- Refractive index Extended
- n = sin i ÷ sin rno unit
- Critical angle Extended
- n = 1 ÷ sin cno unit
4 Electricity and magnetism
- Current and charge Extended
- I = Q ÷ tI in A, Q in C, t in s
- Electromotive force Extended
- E = W ÷ QV
- Potential difference Extended
- V = W ÷ QV
- Resistance
- R = V ÷ IΩ
- Resistors in series
- R = R₁ + R₂ + …Ω
- Two resistors in parallel Extended
- 1 ÷ R = 1 ÷ R₁ + 1 ÷ R₂ΩThe combined resistance is less than either resistor alone.
- Potential divider Extended
- R₁ ÷ R₂ = V₁ ÷ V₂no unit (ratio)
- Electrical power
- P = IVW
- Electrical energy
- E = IVtJ (kWh for household energy)
- Transformer turns
- Vₚ ÷ Vₛ = Nₚ ÷ Nₛno unit (ratio)
- 100% efficient transformer Extended
- IₚVₚ = IₛVₛW
- Power lost in cables Extended
- P = I²RW
6 Space physics
- Average orbital speed Extended
- v = 2πr ÷ Tv in m/s (or km/s), r = orbit radius, T = orbital period
- Hubble constant Extended
- H₀ = v ÷ dper second (current estimate 2.2 × 10⁻¹⁸ /s)
- Age of the Universe (estimate) Extended
- d ÷ v = 1 ÷ H₀s
How to learn them
- Learn each equation with its units, not just the letters. Many marks are lost for a missing or wrong unit.
- Practise rearranging: cover one quantity and write the equation for it.
- Convert to base units before you substitute (g → kg, cm → m, kJ → J, minutes → seconds).
Questions students ask
Do you get a formula sheet in IGCSE Physics?
No. You must recall and use the equations listed in the syllabus.
Which equations are Extended only?
Those marked Extended are in the Supplement column of the syllabus, for example F = ma, Eₖ = ½mv² and n = sin i ÷ sin r.