AC real, reactive and apparent power calculator

Sinusoidal single-phase apparent, real and reactive power.

circuits-reactive-power.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	apparentVA	realPowerW	reactiveV*A
	460	398.372	230
	368	318.697	184

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

real power budget398.37 W✓ passes

BASELINE INPUTS

voltage230 Vcurrent2 Aphase30 deg

CALCULATED

apparent460 VA

realPower398.37 W

reactive230 V*A

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# AC real, reactive and apparent power
# Scope: Sinusoidal single-phase apparent, real and reactive power.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

voltage = 230 V
current = 2 A
phase = 30 deg

apparent := voltage*current [VA]
realPower := voltage*current*cos(phase) [W]
reactive := voltage*current*sin(phase) [V*A]

check real power budget: realPower <= 450 W

scenario alternative: voltage = 184 V

Calculated from your source · not saved

Baseline · Baseline

real power budget398.37 W ✓ passes

alternative · alternative

real power budget318.70 W ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

apparent: apparent = voltage*current [VA]
real power: realPower = voltage*current*cos(phase) [W]
reactive: reactive = voltage*current*sin(phase) [V*A]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

voltage: 230 V
current: 2 A
phase: 30 deg

Calculated

apparent: 460 VA
real power: 398.372 W
reactive: 230 V*A

Assumptions and limits

Sinusoidal single-phase apparent, real and reactive power.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: AC real, reactive and apparent power. Inputs: RMS voltage/current; phase or power factor. Outputs: P, Q, S; power factor. Model scope: Ideal or parameterized lumped components. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: RMS voltage/current, phase or power factor
Outputs: P, Q, S, power factor
Modes: calculate, compare, sweep
Drawing: Schematic and waveform

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS