Electronics
Electrical Power (P = VI)
Feed in RMS voltage, current, power factor, and system type to see real power (kW), apparent power (kVA), and reactive power (kVAR).
Calculate real, apparent, and reactive power for single- or three-phase circuits using P = VI.
AC power triangle
S = V·I·(√3 for 3φ) P = S × PF Q = √(S² − P²)
The calculator multiplies by √3 whenever you choose three-phase, so you only worry about line-to-line voltage and line current inputs.
How to use
- Select single-phase or three-phase.
- Enter voltage, current, and power factor.
- Review kW, kVA, kVAR, and the resulting power factor to size conductors or transformers appropriately.
Example
Input: Three-phase, 480 V, 40 A, PF = 0.92
Output: Real ≈ 30.6 kW, Apparent ≈ 33.3 kVA, Reactive ≈ 13.1 kVAR
Student-friendly breakdown
This walkthrough emphasizes the most searched ideas for Electrical Power (P = VI): Electrical Power (P = VI). Start with the formula above, then follow the guided steps to double-check your work. For quick revision, highlight the givens, plug into the equation, and finish by verifying your units.
Need more support? Use the links below to open the long-form guide, browse additional examples, or hop into adjacent calculators within the same topic — each one is a quick way to double-check your work or handle a related question without starting from scratch.
Deep dive & study plan
Electrical Power (P = VI): Calculates real, apparent, and reactive power for single- or three-phase systems. It's built around kW, kVA, three phase, so you can go from a raw question to a checked answer without switching tools.
The math behind it: The calculator multiplies by √3 whenever you choose three-phase, so you only worry about line-to-line voltage and line current inputs. The core relationship is S = V·I·(√3 for 3φ) P = S × PF Q = √(S² − P²), shown above the calculator so you can see exactly how your inputs turn into the result.
To use it well: (1) Select single-phase or three-phase. (2) Enter voltage, current, and power factor. (3) Review kW, kVA, kVAR, and the resulting power factor to size conductors or transformers appropriately. Keep your units consistent as you go, and re-run a case you already know the answer to — it's the fastest way to catch a typo before it throws off a result you're relying on.
Worked example: entering Three-phase, 480 V, 40 A, PF = 0.92 returns Real ≈ 30.6 kW, Apparent ≈ 33.3 kVA, Reactive ≈ 13.1 kVAR. Try swapping in your own numbers next, especially a case you're unsure about, before you use this for something that matters.
Quick retention checklist
- Speak the formula aloud (or annotate it) so the relationships stick.
- Write each step in your own words and compare with the numbered list above.
- Swap in new numbers for the Example to make sure the calculator (and your logic) handles edge cases.
- Check at least one related calculator below — it's the fastest way to confirm your numbers still line up from a different angle.
FAQ & notes
Does it handle line-to-neutral measurements?
Yes. Use the voltage and current measured at the same point. For three-phase, enter line-to-line voltage and line current.
Can PF exceed 1?
No. Power factor is limited to ±1. The slider clamps inputs between 0 and 1 to keep calculations within physical bounds.
What formula does the Electrical Power (P = VI) use?
The calculator multiplies by √3 whenever you choose three-phase, so you only worry about line-to-line voltage and line current inputs.
How do I use the Electrical Power (P = VI)?
Select single-phase or three-phase. Enter voltage, current, and power factor. Review kW, kVA, kVAR, and the resulting power factor to size conductors or transformers appropriately.