Amp Volt Watt Calculator

Amp Volt Watt Calculator

Amp Volt Watt Calculator

Professional electrical calculator for voltage, current, resistance, and power calculations using Ohm’s Law and power formulas

💡 Enter any 2 values to calculate the other 2 values automatically
Volts (V)
Electrical potential difference
Amperes (A)
Electrical current flow
Ohms (Ω)
Electrical resistance
Watts (W)
Electrical power consumption
⚙️ Advanced Options

🔌 Component Database

Select a common electrical component to auto-fill typical values:

⚡ Three-Phase Circuit Calculations

Calculate three-phase power systems with power factor considerations:

Volts (V)
Three-phase line-to-line voltage (e.g., 480V, 208V, 400V)
Volts (V)
Phase voltage (VLN = VLL / √3)
Decimal (0.0 – 1.0)
Typical: 0.8-0.9 (motors), 1.0 (unity), 0.95+ (corrected)
Most common: Wye for 4-wire systems, Delta for 3-wire
Three-Phase Power Formulas:
Real Power: P = √3 × VLL × I × PF
Apparent Power: S = √3 × VLL × I
Reactive Power: Q = √3 × VLL × I × sinθ
Line-to-Neutral: VLN = VLL / √3
Standard Three-Phase Voltages:
208V: 120V line-to-neutral (4-wire wye)
240V: 139V line-to-neutral (3-wire delta)
400V: 230V line-to-neutral (4-wire wye)
480V: 277V line-to-neutral (4-wire wye)
Amp Volt Watt Calculator
Table of Contents

What is the Relationship Between Amps, Volts, and Watts?

Amps (amperes), volts, and watts are the three fundamental units in electrical engineering that describe how electricity behaves in circuits. Understanding their relationship is essential for anyone working with electrical systems, from hobbyists to professional electricians.

Voltage (V) is the electrical pressure that pushes current through a circuit. Think of it like water pressure in a pipe—higher voltage means more “push” to move electrons.

Current (I) measured in amperes (amps) is the flow rate of electrical charge. Using the water analogy, current is like the flow rate of water through a pipe.

Power (P) measured in watts is the rate at which electrical energy is consumed or converted. It represents the actual work being done by electricity—lighting a bulb, running a motor, or charging a battery.

Ohm’s Law – Voltage, Current, and Resistance
V = I × R
Voltage equals current multiplied by resistance. This fundamental law discovered by Georg Ohm in 1827 shows how these three quantities relate in any electrical circuit.
Power Formula – Watts from Volts and Amps
P = V × I
Power equals voltage multiplied by current. This formula tells you how much electrical energy is being used or produced in a circuit.
Alternative Power Formulas
P = I² × R   |   P = V² ÷ R
These derived formulas let you calculate power when you know different combinations of voltage, current, and resistance.
Volts to Amps Calculator Amps to Volts Calculator Amps to Watts Calculator Watts to Ohms Calculator Watt-Hour Calculator Ohm’s Law Calculator

Practical Examples

💡 Example 1: LED Light Bulb
Scenario: A 10W LED bulb operates on 120V household voltage.

Calculation:
Current (I) = Power ÷ Voltage
I = 10W ÷ 120V = 0.083A (83 milliamps)
Resistance (R) = Voltage ÷ Current
R = 120V ÷ 0.083A = 1,446Ω

Application: This low current draw is why LED bulbs are so energy-efficient compared to traditional incandescent bulbs that draw much more current for the same light output.
🔌 Example 2: Space Heater
Scenario: A 1,500W space heater plugged into a 120V outlet.

Calculation:
Current (I) = Power ÷ Voltage
I = 1,500W ÷ 120V = 12.5A
Resistance (R) = Voltage ÷ Current
R = 120V ÷ 12.5A = 9.6Ω

Application: This high current draw (12.5A) explains why space heaters require dedicated 15A or 20A circuits and why you shouldn’t plug multiple high-power devices into the same outlet.
🔋 Example 3: USB Charging
Scenario: A smartphone charger provides 5V at 2A.

Calculation:
Power (P) = Voltage × Current
P = 5V × 2A = 10W
Resistance (R) = Voltage ÷ Current
R = 5V ÷ 2A = 2.5Ω

Application: This 10W power delivery is why modern USB charging has evolved to higher voltages (USB-C Power Delivery can go up to 20V at 5A for 100W) to charge devices faster without increasing current to unsafe levels.
⚙️ Example 4: Industrial Motor
Scenario: A 480V industrial motor drawing 20A.

Calculation:
Power (P) = Voltage × Current
P = 480V × 20A = 9,600W (9.6 kW)
Resistance (R) = Voltage ÷ Current
R = 480V ÷ 20A = 24Ω

Application: Industrial systems use higher voltages to reduce current for the same power output, which minimizes energy loss in wiring and reduces the size of conductors needed.

⚠️ Safety Notice

This calculator provides theoretical calculations for educational and planning purposes. Working with electrical systems can be dangerous and should only be performed by qualified individuals following proper safety procedures and local electrical codes. Always consult with licensed electricians for installations and repairs.

Author

  • Manish Kumar

    Manish holds a B.Tech in Electrical and Electronics Engineering (EEE) and an M.Tech in Power Systems, with over 10 years of experience in Metro Rail Systems, specializing in advanced rail infrastructure.

    He is also a NASM-certified fitness and nutrition coach with more than a decade of experience in weightlifting and fat loss coaching. With expertise in gym-based training, lifting techniques, and biomechanics, Manish combines his technical mindset with his passion for fitness.

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