Power Calculator: Instantly Compute Wattage from Work and Time
Use this online power calculator to convert work (joules) and time (seconds) into power (watts) in one click. Type any positive values, press “Calculate,” and the tool returns wattage rounded to two decimals. One watt equals one joule of energy transferred every second (NIST, 2019).
Power Calculator
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How to use the tool
Enter work done (J): e.g., 9 500 J or 42 300 J.
Enter time (s): e.g., 18 s or 240 s.
Click “Calculate”: the result appears instantly in watts with two-decimal precision.
Check validity: both inputs must be positive; the tool rejects negatives or zeros.
Formula used
Power equals work divided by time:
$$P = rac{W}{t}$$
P = power (W)
W = work (J)
t = time (s)
Example calculations
Example A: 9 500 J ÷ 18 s = 527.78 W.
Example B: 42 300 J ÷ 240 s = 176.25 W.
Quick-Facts
The SI unit of power is the watt (W); 1 W = 1 J s⁻¹ (NIST, 2019).
An average adult at rest outputs ≈ 100 W of metabolic power (NASA Human Integration Design Handbook, 2010).
EU Ecodesign limits standby consumption to < 0.5 W for most devices (EU Regulation 1275/2008).
Digital power meters reach ±0.1 % accuracy (Keysight P-Series Datasheet, 2022).
FAQ
What is power?
Power measures how fast energy changes form; one watt equals one joule each second (NIST, 2019).
Why should I use this calculator?
It eliminates manual division, reduces rounding errors, and shows results to 0.01 W for clear comparisons (Keysight Datasheet, 2022).
Which units can I enter?
Enter work in joules and time in seconds. The calculator converts only these SI units to maintain consistency (NIST, 2019).
How precise is the result?
The tool rounds to two decimals; underlying float math keeps error below 0.01 % for typical inputs (Mozilla JS Docs, 2023).
Can I convert watts to horsepower?
Yes; divide watts by 746 to obtain mechanical horsepower per SAE J1349 (SAE, 2015).
Who is the watt named after?
The unit honours James Watt, inventor of the modern steam engine (Royal Society Biography, 2021).
Do small standby loads matter?
“Even half-watt idle draws become significant when multiplied by billions of devices” (EU Commission, 2020).
How does the formula change for average power over varying loads?
Integrate instantaneous power over the interval and rac by total time: $$P_{avg}= rac{1}{t_2-t_1}\int_{t_1}^{t_2}P(t)\,dt$$ (MIT OpenCourseWare, 2018).
Important Disclaimer
The calculations, results, and content provided by our tools are not guaranteed to be accurate, complete, or reliable. Users are responsible for verifying and interpreting the results. Our content and tools may contain errors, biases, or inconsistencies. We reserve the right to save inputs and outputs from our tools for the purposes of error debugging, bias identification, and performance improvement. External companies providing AI models used in our tools may also save and process data in accordance with their own policies. By using our tools, you consent to this data collection and processing. We reserve the right to limit the usage of our tools based on current usability factors. By using our tools, you acknowledge that you have read, understood, and agreed to this disclaimer. You accept the inherent risks and limitations associated with the use of our tools and services.
