Library / Tools / Physics equation calculator / Energy transferred (E = Pt)

Energy transferred (E = Pt) calculator

GCSEA-level Energy and power

The energy transferred by a device is its power multiplied by the time it is on.

E = P t

This free calculator is for GCSE and A-level physics. Choose the quantity you want to find, enter the other values with their units, and it shows the working in the layout used in exams, with the answer to the number of significant figures you choose. The values shown are an example. Change them to your own.

Quantity to find

EEnergy transferred to find 3.60 × 10⁵ J

PPower

tTime

Significant figures

Working

Write the equation
E = P t
Substitute the values
E = 2000 × 180
Calculate
E = 3.6 × 10⁵ J
Give the answer to 3 significant figures
E = 3.60 × 10⁵ J

Worked example

Find E, the energy transferred. Given: power P = 2000 W; time t = 180 s.

Write the equation
E = P t
Substitute the values
E = 2000 × 180
Calculate
E = 3.6 × 10⁵ J
Give the answer to 3 significant figures
E = 3.60 × 10⁵ J

Symbols and units

Symbol	Quantity	SI unit
E	Energy transferred	J
P	Power	W
t	Time	s

Energy transferred (E = Pt): rearranged

To find energy transferred: E = P t
To find power: P = E / t
To find time: t = E / P

Exam tip

For energy bills, kWh is power in kW times time in hours. This calculator can give an answer in kWh.

Common questions

What is the formula for energy transferred?

The equation is E = P t, where E is the energy transferred (J); P is the power (W); t is the time (s).

What units should I use for energy transferred?

In SI units: energy transferred in J, power in W, time in s. The calculator also accepts common alternatives such as kilometres, grams or minutes, and converts them for you.

How do I rearrange E = P t?

Rearranging gives these forms: to find energy transferred: E = P t. to find power: P = E / t. to find time: t = E / P.

Practise energy transferred (e = pt) questions

Include unit conversions (km, g, minutes…)

Press the button for a question with random numbers. Work it out on paper first, then type your answer.

More energy and power equations: Work done, Work done by an angled force, Elastic potential energy, Power from force and speed, Kinetic energy, Gravitational potential energy, Power, Efficiency. See the full list on the physics equation calculator page.