Electrical Power Calculator (DC, 1φ, 3φ)
Real, apparent and reactive power for DC, single-phase and three-phase systems with power factor — plus kWh per day.
Your electricity meter bills REAL power (kWh), but wires, breakers and transformers are sized by APPARENT power (VA) — that is why a poor power factor costs industry money and why a “600 W” UPS is also rated “1000 VA”. For 3-phase, this assumes a balanced load; measure per-phase if unsure.
Electrical Power Calculator computes real, apparent and reactive power for DC, single-phase and three-phase loads — free, instant and private in your browser. Electricians, plant engineers and students sizing supplies and decoding nameplates use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Electrical Power Calculator (DC, 1φ, 3φ)
Electrical Power Calculator computes real, apparent and reactive power for DC, single-phase and three-phase loads using the standard engineering relation: DC: P = VI; 1φ: P = VI·PF; 3φ: P = √3·V(LL)·I·PF; Q = √(S² − P²). Worked live: a 3-phase motor at 415 V, 5 A, PF 0.9 draws 3.23 kW real out of 3.59 kVA apparent. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Electrical Power Calculator (DC, 1φ, 3φ)
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Electrical Power Calculator (DC, 1φ, 3φ)?
- ✓Implements the real formula — DC: P = VI — with the substitution shown, not a black box
- ✓Built for electricians, plant engineers and students sizing supplies and decoding nameplates
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate electrical power?+
Real, apparent and reactive power for DC, single-phase and three-phase loads follows DC: P = VI; 1φ: P = VI·PF; 3φ: P = √3·V(LL)·I·PF; Q = √(S² − P²). For example, a 3-phase motor at 415 V, 5 A, PF 0.9 draws 3.23 kW real out of 3.59 kVA apparent. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
What's the difference between kW and kVA?+
kW is real power that does work and bills on your meter; kVA is apparent power that sizes the wires, breakers and transformers. They differ by the power factor — a 0.8 PF load needs 25 % more kVA than its kW, which is why UPSes carry both ratings.
Why is there a √3 in three-phase power?+
Because line-to-line voltage is √3 times the phase voltage in a balanced system. Using V(LL) — what a meter reads between phases — the total of all three phases collapses to √3·V(LL)·I·PF.
Is the Electrical Power Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
Related Electronics tools
PCB Trace Width Calculator (IPC-2221)
Minimum trace width for your current and temperature rise — IPC-2221 formula with copper weight, layer choice and a step-by-step worked example.
● LiveMicrostrip Impedance Calculator
Z₀ of a surface microstrip from width, height and εr (IPC-2141A), plus effective dielectric constant and propagation delay.
● LiveStripline Impedance Calculator
Characteristic impedance of an embedded stripline trace from geometry and εr — the inner-layer companion to the microstrip tool.
● Live