Free online electrical power calculator to calculate power (watts), voltage (volts), current (amperes), and resistance (ohms). Use electrical power formulas P = V × I, P = V²/R, and P = I²R with step-by-step solutions.
Calculate electrical power, voltage, current, or resistance using power formulas
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Electrical power is a fundamental concept in physics and electrical engineering, representing the rate at which electrical energy is transferred, converted, or consumed in a circuit. Measured in watts (W), electrical power is crucial for designing circuits, sizing components, and understanding energy consumption. Our Electrical Power Calculator makes it easy to calculate power, voltage, current, or resistance using the fundamental electrical power formulas: P = V × I, P = V²/R, and P = I²R.
Whether you're working on electrical circuit design, troubleshooting electrical systems, calculating energy consumption, or solving physics problems, understanding how to calculate electrical power is essential. Our calculator automatically selects the appropriate formula based on the values you provide, making complex electrical power calculations simple and accurate.
Our Electrical Power Calculator is designed for simplicity and accuracy. Follow these steps to calculate electrical power or related values:
The calculator supports multiple electrical power formulas, so you can solve for any missing value regardless of which two values you know. This makes it perfect for circuit analysis, component sizing, and electrical design work.
Electrical power can be calculated using three main formulas, each useful in different scenarios:
P = V × I
Where: P = Electrical Power (W), V = Voltage (V), I = Current (A)
This is the most fundamental electrical power formula. It directly relates electrical power to voltage and current, making it perfect when you know both electrical potential difference and current flow. This formula works for both DC circuits and AC circuits with resistive loads.
P = V²/R
Where: P = Electrical Power (W), V = Voltage (V), R = Resistance (Ω)
This electrical power formula is useful when you know the voltage across a component and its resistance, but not the current. It's derived from combining P = VI with Ohm's Law (V = IR). This formula shows that electrical power is proportional to the square of voltage.
P = I²R
Where: P = Electrical Power (W), I = Current (A), R = Resistance (Ω)
This electrical power formula is ideal when you know the current flowing through a component and its resistance. It shows that electrical power is proportional to the square of current, which is why high-current circuits generate more heat and require proper wire sizing.
You can rearrange these electrical power formulas to solve for any variable:
Our electrical power calculator automatically applies the correct rearrangement based on which values you provide. This makes it easy to solve for any missing parameter in electrical circuit calculations.
Electrical power calculations are essential in countless applications:
Electrical power is measured in watts (W), with common multiples and conversions:
Energy vs. Power: Electrical power (watts) is the rate of energy transfer, while electrical energy (watt-hours, kWh) is the total energy consumed over time. Electrical power × time = electrical energy.
A device operates at 120V and draws 2A of current. What is its electrical power consumption?
P = V × I
P = 120 V × 2 A = 240 W
The device consumes 240 watts of electrical power
A 1000W appliance operates at 120V. What current does it draw?
I = P / V
I = 1000 W ÷ 120 V = 8.33 A
The appliance draws 8.33 amperes of current
A resistor dissipates 50W of electrical power when 5A flows through it. What is its resistance?
R = P / I²
R = 50 W ÷ (5 A)² = 50 ÷ 25 = 2 Ω
The resistor has a resistance of 2 ohms
A 100W light bulb has a resistance of 144Ω. What voltage is required?
V = √(P × R)
V = √(100 W × 144 Ω) = √14400 = 120 V
The light bulb requires 120 volts
Our electrical power calculator works for both AC and DC circuits:
For most practical applications with resistive loads (lights, heaters, motors), our electrical power calculator provides accurate results for both AC and DC circuits.
Electrical power is the rate at which electrical energy is transferred or consumed, measured in watts (W). It's calculated using P = V × I (voltage times current), P = V²/R (voltage squared divided by resistance), or P = I²R (current squared times resistance). Our electrical power calculator can solve for any variable using these formulas.
Electrical power (watts) is the rate of energy transfer, while electrical energy (watt-hours, kWh) is the total energy consumed over time. Power × time = energy. For example, a 100W device running for 10 hours consumes 1000 watt-hours (1 kWh) of electrical energy.
Simply multiply voltage by current: P = V × I. For example, if a device operates at 120V and draws 2A, its electrical power is 120 × 2 = 240W. This is the most common electrical power calculation method.
Yes! Our electrical power calculator works for both AC and DC circuits when using resistive loads. For AC circuits, use RMS (root mean square) values for voltage and current. For circuits with reactive components (capacitors, inductors), additional power factor considerations may be needed.
Divide electrical power by voltage: I = P / V. For example, a 1000W device at 120V draws 1000 ÷ 120 = 8.33A. This calculation is essential for sizing circuit breakers and wire gauges.
Electrical power dissipated in a resistor is converted to heat. The formula P = I²R shows that power (and thus heat generation) is proportional to the square of current. This is why high-current circuits require larger wire gauges and better heat dissipation.
You can calculate resistance using R = V²/P (if you know voltage and power) or R = P/I² (if you know current and power). For example, if a resistor dissipates 50W at 10V, its resistance is (10)²/50 = 100/50 = 2Ω.
Standard SI units: volts (V) for voltage, amperes (A) for current, ohms (Ω) for resistance, and watts (W) for electrical power. Common multiples include kilowatts (kW) for larger values and milliwatts (mW) for smaller values.
Understanding electrical power and how to calculate it is fundamental to electrical engineering, circuit design, and energy management. Our Electrical Power Calculator simplifies these calculations, making it easy to determine power, voltage, current, or resistance for any electrical circuit.
Whether you're designing circuits, sizing components, calculating energy consumption, or solving physics problems, this calculator provides accurate results with step-by-step solutions. Ready to explore more electrical concepts? Check out our other calculators like the Watt Calculator for additional power calculations, or use our Wire Size Calculator to determine appropriate wire gauges based on current and electrical power requirements.
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