Watt to Volt Calculator

Convert between watts and volts using Ohm's Law. Supports single-phase and three-phase systems. Essential electrical engineering tool for students and professionals.

Single-Phase
Power & Current
V = P / I
Single-Phase
Power & Resistance
V = √(P × R)
Single-Phase
Power from Voltage
P = V² / R
Three-Phase
Power Calculation
P = √3 × V × I × PF
Three-Phase
Current Calculation
I = P / (√3 × V × PF)

Electrical Power Formulas:

Single-Phase: P = V × I

Three-Phase: P = √3 × V × I × PF

Ohm's Law: V = I × R

Where for single-phase: V = Phase Voltage, I = Phase Current

Where for three-phase: V = Line Voltage, I = Line Current, PF = Power Factor

√3 ≈ 1.732 (Square root of 3 for three-phase calculations)

Electrical power consumption or output
Resistance in the electrical circuit
Light Bulb (240Ω)
Resistor (1kΩ)
Heater Element (10Ω)
Speaker (50Ω)
Calculation Results
Input Values
Power
100.000 W
Resistance
50.000 Ω
Calculation Mode
Single-Phase: Power & Resistance
Formula Used
V = √(P × R)
Voltage equals the square root of Power times Resistance
Calculation Result
Voltage
70.71
Volts (V)
Step-by-Step Calculation
1. Given: P = 100.00 W, R = 50.00 Ω
2. Formula: V = √(P × R)
3. Calculation: V = √(100.00 × 50.00)
4. Calculation: V = √(5000.00)
5. Result: V = 70.71 V
Power (W)
Voltage (V)
Current (A)
Three-Phase

Understanding Electrical Power Calculations

Electrical power calculations are fundamental in electrical engineering and electronics. Understanding the relationship between voltage, current, resistance, and power is essential for designing, analyzing, and troubleshooting electrical circuits.

Ohm's Law:

V = I × R

Where V is voltage in volts, I is current in amperes, and R is resistance in ohms. This fundamental law describes the relationship between voltage, current, and resistance in an electrical circuit.

Three-Phase Power Systems:

Three-phase systems are commonly used for power generation, transmission, and distribution, especially for industrial and commercial applications. The key advantages include:

  • More power delivery with less conductor material
  • Constant power transfer (no power pulsations)
  • Ability to directly drive three-phase motors
  • More efficient power transmission

Power Formulas

System Type Formula Explanation
Single-Phase AC/DC P = V × I Power equals voltage multiplied by current
Three-Phase (Balanced) P = √3 × VL × IL × PF Three-phase power with power factor
Three-Phase (Unbalanced) P = VaIa + VbIb + VcIc Sum of powers in each phase
Apparent Power (S) S = V × I (single)
S = √3 × V × I (three) 		Product of voltage and current
Reactive Power (Q) Q = √(S² - P²) Power stored and released by inductive/capacitive loads

Power Factor in Three-Phase Systems

1

Definition: Power factor (PF) is the ratio of real power (kW) to apparent power (kVA). It represents how effectively electrical power is being used.

2

Typical Values: Resistive loads have PF = 1.0. Induction motors typically have PF = 0.7-0.9. Fluorescent lights have PF = 0.5-0.9. Power factor correction capacitors can improve PF to near 1.0.

3

Importance: Low power factor increases current for the same real power, causing higher losses in transmission lines and requiring larger equipment. Many utilities charge penalties for low power factor.

Common Electrical Standards

1

Residential Voltage: Most countries use either 110-120V or 220-240V for household electrical systems. North America typically uses 120V, while Europe and most of Asia use 230V.

2

Industrial Three-Phase: Common three-phase voltages include 208V (US), 400V (EU), 480V (US industrial), and 600V (Canada). Higher voltages like 6.6kV and 11kV are used for large industrial facilities.

3

Current Capacity: Standard household circuits are typically rated for 15A or 20A. Industrial three-phase circuits can range from 20A to several thousand amps for large installations.

Applications of Electrical Calculations

  • Circuit Design: Determining component ratings and specifications
  • Energy Efficiency: Calculating power consumption and optimizing efficiency
  • Safety Analysis: Ensuring circuits operate within safe limits
  • Power Supply Design: Designing transformers, regulators, and converters
  • Renewable Energy: Sizing solar panels, batteries, and inverters
  • Industrial Applications: Sizing motors, transformers, and distribution systems

Calculator Features:

  • Three single-phase calculation modes: Power & Current, Power & Resistance, and Power from Voltage
  • Two three-phase calculation modes: Power Calculation and Current Calculation
  • Supports multiple units (W, kW, mW, A, mA, V, kV, mV, Ω, kΩ, MΩ)
  • Power factor slider for three-phase calculations (0.5 to 1.0)
  • Provides step-by-step calculation explanations
  • Visualizes relationships with interactive charts
  • Includes common example values for quick testing

Frequently Asked Questions

Single-phase power uses two wires (phase and neutral) and delivers power in pulses. Three-phase power uses three or four wires (three phases and sometimes neutral) and delivers continuous power. Three-phase systems are more efficient for power transmission and can directly run three-phase motors, making them ideal for industrial applications.

For three-phase systems, the formula for power is P = √3 × V × I × PF, where √3 ≈ 1.732, V is line-to-line voltage, I is line current, and PF is power factor. To calculate voltage: V = P / (√3 × I × PF). This calculator includes both three-phase power and current calculations.

Power factor (PF) is the ratio of real power (kW) to apparent power (kVA). It represents how effectively electrical power is being converted into useful work. Low power factor increases current for the same real power, causing higher losses and requiring larger equipment. In three-phase systems, power factor is crucial for accurate power calculations and system efficiency.

Yes, the single-phase formulas work for both AC and DC circuits. However, for AC circuits with reactive components (inductors or capacitors), you need to consider power factor for accurate power calculations. The calculator assumes resistive loads (power factor = 1) for single-phase AC unless otherwise specified.

Common three-phase voltage standards include:
  • 120/208V (US commercial buildings)
  • 277/480V (US industrial)
  • 230/400V (Europe residential/commercial)
  • 400/690V (Europe industrial)
  • 240/415V (Australia, UK)
  • 347/600V (Canada industrial)
The first number is phase-to-neutral voltage, the second is phase-to-phase (line) voltage.