Example 1
The kettle heats water for tea: 300000 J delivered in 150 s. Exactly the working pace of a solid 2 kW kettle.
Power from work and time calculator
Type work W [J] and time t [s]. The calculator computes power P = W/t. 300,000 J in 150 s is 2000 W, or 2 kW. 15,000 J in 60 s is 250 W. Zero seconds does not divide.
Work: W = F·s. Circuit power: P = U·I.
Result
Work (J) and Time (s). Power shows up here.
How it works
P = W/t. A kettle 300,000 J in 150 s: P = 2000 W = 2 kW. A cyclist 15,000 J in 60 s: P = 250 W. The same work in a shorter t is higher power. A travel kettle 120,000 J in 180 s is about 667 W. A lift 50,000 J in 20 s is 2500 W. A vacuum 900,000 J in 600 s is 1500 W. An LED 36,000 J in 3600 s is 10 W. A dryer 600,000 J in 300 s is 2 kW. A pump 800 J in 40 s is 20 W.
Fields: W in joules, t in seconds. Result in watts, 1 W = 1 J/s. 1000 W = 1 kW. t must be positive. Zero seconds does not divide. A comma and a period are the same t: 150,5 and 150.5. Typed 0 in W gives P = 0. Both fields need a number before 2 kW can appear. 2 kW is the result, not the W input: the field wants joules, not kilowatts.
You can take work W from W = F·s or from energy you already know. Ep = m g h while lifting is often close to W if F ≈ m g. This calculator does not ask for F or s.
P = U·I lives on circuit power. Volts and amperes there, joules and seconds here. Both results are in watts, but the inputs differ. A 2 kW kettle on P = U·I is, for example, 230 V and about 8.7 A, not 300,000 in the W field.
Mean power over the whole interval t. Instant peaks on a P(t) plot do not sit here. The model is P = W/t, one work, one time.
Type 300000 and 150, click Calculate, and match 2000 W. Then 15000 and 60 for 250 W. The header symbol does not heat the water.
How to use
- Type work W in joules, for example 300000. That is joules, not kilowatts.
- Type time t in seconds, for example 150. Zero will not run, because you divide by t.
- Click Calculate. 300000 J and 150 s give 2000 W = 2 kW. 15000 J and 60 s give 250 W.
- t must be positive. Typed 0 in W gives P = 0. Both fields need a number.
- For P = U·I, open circuit power. Work W = F·s is next door.
Formula
P = W ÷ t
P, W, and t at 300,000 J
Mechanical power in this calculator is P = W/t. 300,000 J in 150 s is 2000 W = 2 kW. Field W wants work [J], not the kilowatt result.
- P
- Power [W]. 15,000 J in 60 s is 250 W. 36,000 J in 3600 s is 10 W. 1 W = 1 J/s.
- W
- Work [J], first field. 2 kW is the result, not the input. 800 J in 40 s is 20 W.
- t
- Time [s]. Zero does not divide. 120,000 J in 180 s is about 667 W.
- kW
- 1000 W. 300,000 J in 150 s and 600,000 J in 300 s both give 2 kW.
Real-life examples
Example 2
A tiny travel kettle at the campsite: 120000 J over 180 s. Same cup of tea, just a bit more patience required.
Example 3
The lift hauls a loaded cab up one floor: 50000 J of work in 20 s. The rooftop motor does not even break a sweat.
Example 4
A cyclist grinding up a climb: 15000 J in 60 s, around 250 W. What a fit amateur can hold for a good while.
Example 5
The Saturday vacuuming session: 900000 J in 600 s. A 1.5 kW machine running for a full ten minutes.
Example 6
An LED bulb glowing for an hour: 36000 J over 3600 s. A modest 10 W that makes old filament bulbs look like heaters.
Example 7
Drying hair after the pool: 600000 J in 300 s. A 2 kW dryer working flat out for five full minutes.
Example 8
Topping up a tyre before a ride: 800 J of pumping in 40 s. Tiny power on paper, yet your arms file a complaint.
Example 9
A winch hoisting its load: 12000 J in just 15 s. A short burst where the motor gets to show its character.
Example 10
A runner attacking a short hill: 20000 J in 50 s. A brief surge of power that the lungs invoice immediately.
Example 11
Whipping cream with a hand mixer: 54000 J over 180 s. A steady 300 W of spinning until the peaks finally hold.
Example 12
A crate hoisted onto the rack: 2000 J of work in 5 s. One short, decisive effort instead of a long slog.
Frequently asked questions
What is P at 300,000 J and 150 s?
Power is 2000 W, or 2 kW. You divide the 300,000 J of work by 150 s, and a watt is one joule per second: 1 W = 1 J/s.
What about 15,000 J and 60 s?
You get 250 W. At 800 J and 40 s the result is 20 W, and at 36,000 J in an hour (3600 s) it stays 10 W.
Which units do I type?
Work W [J], time t [s]. Result P [W]; 1000 W is 1 kW, and 1 W = 1 J/s.
How is this different from P = U·I?
Here power comes from work and time. There you compute circuit power from volts and amperes. Both results are in watts, but the fields differ.
Is 2 kW the number 2000 in field W?
No. Field W wants work [J], not kilowatts of the result. 2 kW appears after the division, when 300,000 J lasts 150 s.
Where do I get W?
From the W = F·s card, or from energy you already know in the problem. For lifting, Ep = m g h is often close, but that is another formula.
What about 120,000 J and 180 s?
Power is about 667 W. The same card at 50,000 J in 20 s gives 2500 W, and at 900,000 J in 600 s gives 1500 W.
Does a comma in 150,5 work?
Yes. 150.5 and 150,5 are the same time t [s]. The calculator does not insist on a period.
What is 1 W?
One watt is one joule per second. A thousand watts is 1 kW, so a 2000 W kettle is 2 kW.
What about 600,000 J and 300 s?
Again 2000 W, or 2 kW. Twice the work in twice the time gives the same power as 300,000 J in 150 s.
Knowledge sources
The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.
Page updated in 2026.