Calculator Inputs
Formula Used
- Single-Phase AC: S = V × I (Volt-Ampere)
- Three-Phase AC: S = √3 × VL × IL (line values)
- Real Power (AC): P = S × PF
- Reactive Power (AC): Q = S × √(1 − PF²)
- DC: P = V × I and VA = W
Tip: Apparent power (VA) is used for transformer, inverter, and generator sizing. Real power (W) describes useful work, and reactive power (VAR) relates to inductive or capacitive loading.
How to Use This Calculator
- Select your circuit type (single-phase, three-phase, or DC).
- Enter voltage and current, then choose units if needed.
- For AC, optionally enter power factor to estimate watts and vars.
- Click Calculate to view results above the form.
- Use the CSV or PDF buttons to export the last result.
Example Data Table
| Case | Mode | Voltage | Current | PF | Apparent Power | Real Power |
|---|---|---|---|---|---|---|
| 1 | Single-Phase AC | 230 V | 5 A | 0.90 | 1.15 kVA | 1.035 kW |
| 2 | Three-Phase AC | 400 V | 10 A | 0.85 | 6.928 kVA | 5.889 kW |
| 3 | DC | 48 V | 20 A | — | 960 VA | 960 W |
Values above are illustrative examples for quick reference.
FAQs
1) What does volt-ampere mean?
Volt-ampere (VA) is apparent power. It equals voltage multiplied by current and is used to size electrical equipment like transformers and inverters.
2) Is VA the same as watts?
Not always. In DC or purely resistive loads, VA equals watts. In AC with reactive loads, watts are lower than VA unless power factor is 1.
3) How do I calculate kVA?
Compute VA first, then divide by 1000. This calculator automatically formats results into VA, kVA, or MVA based on magnitude.
4) What formula is used for three-phase apparent power?
For balanced three-phase systems, apparent power is S = √3 × VL × IL, using line-to-line voltage and line current.
5) What is power factor and why does it matter?
Power factor (PF) describes how effectively current is converted into useful work. It helps convert apparent power (VA) into real power (W).
6) Can I use this for generator sizing?
Yes. Generators are commonly rated in kVA because they must supply both real and reactive components of power demanded by the load.
7) Why is reactive power shown in VAR?
Reactive power represents energy that oscillates between the source and reactive elements. It affects current draw and equipment sizing even if it does no net work.
8) How do the download buttons work?
After you calculate, the tool stores the latest result in your session. The CSV and PDF buttons export that stored result instantly.