1,200
W
1,200
VA
0
VAR
120
V
10
A
1,200
Wh
1.2
kWh
28.8
kWh/day
864
kWh/month
10,512
kWh/year
1,200
W
1,200
VA
0
VAR
120
V
10
A
1,200
Wh
1.2
kWh
28.8
kWh/day
864
kWh/month
10,512
kWh/year
The ElectriCalc Pro is a comprehensive electrical calculator that consolidates the most essential calculations in electrical engineering and trade work into a single, easy-to-use interface. Rather than switching between a power calculator, an Ohm's Law tool, and a power factor calculator separately, this tool computes all critical values simultaneously — real power, apparent power, reactive power, Ohm's Law derived values, and energy consumption — from four fundamental inputs: voltage, current, resistance, and power factor.
Electrical professionals routinely need to cross-check multiple related quantities when diagnosing circuits, sizing equipment, or verifying calculations. A motor technician checking a three-phase motor might want to verify that the measured current, known supply voltage, and nameplate power factor are consistent with the rated power. An electrician wiring a commercial panel needs to know both real power (for load calculations) and apparent power (for breaker and wire sizing). An energy auditor wants watts and kilowatt-hours simultaneously. ElectriCalc Pro delivers all of this in one computation.
The four fundamental electrical quantities — voltage (V), current (I), resistance (R), and power factor (PF) — are sufficient to derive almost every common single-phase AC electrical quantity. Voltage is the electromotive force driving current through a circuit, measured in volts. Current is the flow rate of electric charge, measured in amperes. Resistance opposes that flow, measured in ohms. Power factor captures the phase relationship between voltage and current in AC circuits, ranging from 0 (purely reactive) to 1.0 (purely resistive / unity).
From these inputs, the calculator derives: Real Power (P = V × I × PF) in watts — the actual power doing useful work; Apparent Power (S = V × I) in volt-amperes — the total power drawn from the source, used for sizing conductors and transformers; Reactive Power (Q = √(S² − P²)) in volt-amperes reactive — the power oscillating in inductive or capacitive elements without doing useful work; Ohm's Law Voltage (V = I × R) — voltage across a resistive element; Ohm's Law Current (I = V ÷ R) — current through a resistive branch; and Energy (1 hour = P ÷ 1000 kWh) — electricity consumption in one hour of operation at the computed real power level.
Understanding the distinction between real, apparent, and reactive power is critical for anyone working with AC systems. Utility billing is based on real power (kWh). Conductor ampacity and transformer ratings are based on apparent power (kVA). Reactive power determines the amount of capacitor correction needed. ElectriCalc Pro shows all three together, reinforcing the power triangle concept central to AC circuit theory.
This calculator is designed for both field use (quick checks on job sites) and educational purposes (students learning AC power concepts). Default values represent a typical 120 V, 10 A resistive load at unity power factor — a simple baseline for exploring how each parameter affects the outputs.
Apparent Power: S = V × I (volt-amperes). This is the product of RMS voltage and RMS current, representing the total power drawn from the supply.
Real Power: P = V × I × PF = S × PF (watts). The power factor scales apparent power to the portion actually doing work.
Reactive Power: Q = √(S² − P²) (VAR). Derived from the power triangle: S² = P² + Q². A purely resistive circuit has Q = 0; inductors and capacitors introduce reactive power.
Ohm's Law Voltage: V_R = I × R. Gives the voltage drop across a resistance R when current I flows through it.
Ohm's Law Current: I_R = V ÷ R. Gives the current through resistance R when voltage V is applied across it.
Energy (1 hour): E = P / 1000 kWh. Kilowatt-hours consumed if the load operates at real power P for one hour.
Real Power (W): What you pay for on your electricity bill. Use this to estimate running costs and for load scheduling.
Apparent Power (VA): Use this for sizing circuit breakers, conductors, and transformers. Always size equipment for apparent power, not real power.
Reactive Power (VAR): Non-zero reactive power indicates an inductive or capacitive load. High reactive power means poor power factor and increased current in conductors. Add capacitor banks to reduce reactive power and improve power factor.
Ohm's Law values: Use V=IR to find voltage drop across a known resistance. Use I=V/R to find branch current. Note these are DC or purely resistive AC values — impedance (Z) must be used for AC circuits with reactance.
Energy (kWh): Multiply by hours of daily operation to get daily consumption. Multiply by your electricity rate ($/kWh) for cost estimation.
Inputs
Results
A 120V, 10A load with 0.85 power factor draws 1200 VA apparent power but only 1020 W real power. The difference (631 VAR reactive) indicates a moderately inductive load. The circuit breaker and wire must be sized for 10 A (apparent), not 8.5 A (real power equivalent).
Inputs
Results
A 240V, 25A motor load at 0.92 PF draws 6000 VA apparent but 5520 W real power. For an 8-hour shift, this consumes 5.52 × 8 = 44.16 kWh. The 35 A breaker (125% of 25 A per NEC 430.52) is the correct protective device.
Watts (W) measure real power — energy actually converted to work or heat. Volt-amperes (VA) measure apparent power — the product of RMS voltage and current regardless of phase angle. In DC circuits and purely resistive AC circuits, VA equals watts. In AC circuits with inductive or capacitive loads, VA is always greater than or equal to watts. Electrical equipment like UPS systems, transformers, and generators are rated in VA or kVA because they must supply the full current demanded, regardless of power factor.
The calculator provides both V=IR and I=V/R simultaneously because they address different use cases. V=IR tells you the voltage drop across a known resistor carrying a known current — useful for checking voltage drops in wiring. I=V/R tells you the current through a resistor when you know the voltage across it — useful for analyzing parallel branches. Having both outputs saves time in complex circuit analysis.
This calculator is designed for single-phase AC. For three-phase systems, real power is P = √3 × V_LL × I × PF (where V_LL is line-to-line voltage), and apparent power is S = √3 × V_LL × I. To adapt this calculator for three-phase, multiply the results by √3 (≈ 1.732) after entering line-to-line voltage and per-phase current.
Typical power factors: resistive heaters 1.0, incandescent lamps 1.0, LED drivers 0.9–0.99, fluorescent lighting with ballasts 0.85–0.95, induction motors (full load) 0.85–0.92, induction motors (partial load) 0.6–0.8, welders 0.5–0.7, arc furnaces 0.7–0.9, large UPS systems 0.8–0.9. When in doubt, use the nameplate PF or measure with a power meter.
The energy output shows kWh consumed in one hour. Multiply by daily operating hours to get daily kWh, then by 30 for monthly consumption. Multiply monthly kWh by your utility rate (e.g., $0.12/kWh) for monthly electricity cost. Example: 1.02 kWh/h × 8 h/day × 30 days × $0.12/kWh = $29.38/month.
Reactive power (VAR) is power that oscillates between the source and inductive/capacitive elements without being consumed. It does no useful work but increases the current that conductors, transformers, and generators must carry. High reactive power means higher I²R losses in wiring, reduced transformer and generator capacity, and potential utility power factor surcharges. Capacitor banks are added to AC circuits to supply reactive power locally, reducing reactive current drawn from the utility.
No. Resistance (R) is the purely real opposition to current flow and dissipates energy as heat. Impedance (Z) is the complex opposition to AC current flow and includes both resistance and reactance: Z = R + jX, where X is the reactance (inductive XL = 2πfL, or capacitive XC = 1/(2πfC)). Ohm's Law in AC circuits uses impedance: V = I × Z. This calculator uses resistance for the Ohm's Law outputs, which is accurate for DC circuits and purely resistive AC loads.
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