Example 1
W = 300000 J, P = 2000 W -> t = 150 s.
Time from work and power
Type work W [J] and power P [W]. The calculator computes time t = W/P: 300,000 J and 2000 W is 150 s, and 3,600,000 J and 500 W is 7200 s. Zero watts does not divide.
Work from power: W = P·t. Power from work: P = W/t.
Result
Work W (J) and Power P (W). The result shows up here.
How it works
Time at steady power is t = W / P. At 300000 J and 2000 W you get 150 s. At 360000 J and 100 W you get 3600 s. At 3600000 J and 500 W you get 7200 s. 1 kWh = 3.6·10^6 J, so 500 W for 7200 s is 1 kWh. 43200 J and 12 W give 3600 s, one hour.
The form has two fields: W in joules and P in watts. The result is in seconds. Type a kilowatt-hour as 3600000, not as 1. A comma and a period are the same P: 1500,5 and 1500.5.
W and P must be positive. Zero does not divide. Both fields need a number before 150 s can appear. This is time at a steady P, not a schedule of power jumps.
W = P t is on the neighbouring page: the same relation, you want W. P = W/t wants power. Ek = ½mv² is another energy, from mass and speed, not from watts.
There is one W, P, t trio. Here the unknown is t. On engine work the unknown is W. On power from work the unknown is P.
Type 300000 and 2000, click Calculate, and match 150 s. The header symbol does not count down minutes. Treat the result as time at that power, not as a trip meter.
How to use
- In the first field enter W in joules, for example 300000. 1 kWh is 3600000 J.
- In the second field enter P in watts, for example 2000. Zero will not run, because you divide by P.
- Click Calculate. The calculator divides W by P. 300000 J and 2000 W give 150 s.
- W and P must be positive. Both fields need a number.
- For W = P·t, open engine work. Power from this pair is on P = W/t. Here it stays t.
Formula
t = W / P
W > 0, P > 0. Unit of t: second.
t, W, and P for work time
Time from energy and power: t = W/P. 300000 J and 2000 W is 150 s. 3600000 J and 500 W is 7200 s. 43200 J and 12 W is 3600 s.
- t
- The unknown time [s]. 300000 / 2000 = 150. One hour is 3600 s at 12 W and 43200 J.
- W
- Work [J]. 3.6e6 J is 1 kWh. W must be positive.
- P
- Power [W]. 2000 W or 500 W. P must be positive, because you divide by it.
Real-life examples
Example 2
W = 360000 J, P = 100 W -> t = 3600 s.
Example 3
W = 3600000 J, P = 500 W -> t = 7200 s.
Example 4
W = 1 J, P = 1 W -> t = 1 s.
Example 5
W = 90000 J, P = 1500 W -> t = 60 s.
Example 6
W = 750000 J, P = 75000 W -> t = 10 s.
Example 7
W = 1800000 J, P = 1000 W -> t = 1800 s.
Example 8
W = 43200 J, P = 12 W -> t = 3600 s.
Ways to use this calculator
- You compute 150 s from 300000 J at 2000 W.
- You check 7200 s from 1 kWh at 500 W.
Frequently asked questions
How much t at 300000 J and 2000 W?
Time is 150 s. You divide 300,000 J by 2000 W. That is the inverse of P = W/t on the power card.
Which units do I type?
Work W [J], power P [W]. Result t [s]. Type 1 kWh as 3,600,000 J, not as 1.
What if P = 0?
The calculator refuses zero watts. t = W/P at zero power does not exist, because you do not divide by zero.
How is this different from W = P·t?
Here you solve for time. There you multiply power by time and get work. Same triple, different unknown.
How is this different from P = W/t?
Here time. There power. The third leg of the same W, P, t triple.
How much at 3600000 J and 500 W?
Time is 7200 s, two hours. 3.6 MJ is 1 kWh, and 500 W spends that kilowatt-hour in 7200 s.
Does a comma in 1500.5 W work?
Yes. 1500.5 and 1500,5 are the same P [W]. A comma and a period mean the same value.
How much at 43200 J and 12 W?
Time is 3600 s, one hour. 12 W for an hour is 43,200 J.
Is Ek = ½mv² the same t?
No. Kinetic energy gives joules you may type as W, but this calculator only finds t after you divide by P.
Is the result in hours?
No. The field and the result are in seconds. 7200 s is two hours, 3600 s is one, but you type seconds.
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.