Average versus instantaneous power
This calculator reports average power over the full time interval. Instantaneous power can be higher or lower during the interval when the work rate changes.
Example
If 600 J of work is done in 30 seconds, average power is 600 / 30 = 20 W.
Common mistakes
Use seconds for time if you want watts from joules. If time is in minutes, multiply by 60 first.
Practical interpretation
A result of 20 W means the process transfers or uses 20 joules each second on average. For electrical devices, use the Electrical Power Calculator when voltage and current are the known inputs.
References
- BIPM SI Brochure, for watt and joule unit definitions.
- NIST SI guidance, for SI derived unit notation.
Last reviewed: 2026-05-17