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Power Calculator – DC & AC | CheckBillOnline.com

Power Calculator

Free online DC & AC power calculator — enter any 2 known values and press Calculate to solve for the others.

DC Power Calculator

Enter any 2 known values and press "Calculate" to solve for the others:

Voltage (V)

Current (I)

Resistance (R)

Power (P)

📊 Calculated Results

Power factor calculator ▶

DC Power Calculation

Voltage (V) calculation from current (I) and resistance (R):

V_(V) = I_(A) × R_(Ω)

Power (P) calculation from voltage (V), current (I) and resistance (R):

P_(W) = V_(V) × I_(A) = V²_(V) / R_(Ω) = I²_(A) × R_(Ω)

📖 How to Use the Power Calculator

The CheckBillOnline.com Power Calculator is a free and easy-to-use online tool designed to help students, electricians, engineers, and homeowners quickly calculate electrical power, voltage, current, and resistance for both DC (Direct Current) and AC (Alternating Current) circuits.

This powerful tool saves you from manual calculations and eliminates errors. Whether you are checking your electricity bill, designing a circuit, troubleshooting an appliance, or studying for an exam, this calculator gives you instant and accurate results.

🔵 For DC Power Calculator:

Enter any 2 of the 4 values: Voltage (V), Current (I), Resistance (R), or Power (P).
Select the correct unit from the dropdown (e.g., volts, millivolts, kilowatts).
Click the "= Calculate" button.
The remaining 2 values are automatically solved and displayed below.
Use the "✕ Reset" button to clear all fields and start fresh.

🔴 For AC Power Calculator:

Enter the magnitudes for Voltage, Current, Impedance, or Apparent Power.
Enter the phase angles θv (voltage angle) and θi (current angle) in degrees.
Click "= Calculate" to get Real Power (P), Reactive Power (Q), Power Factor (PF), and Impedance.
Results are shown instantly in color-coded output boxes.

Tip: If you are checking your electricity bill, use the DC calculator to find how many watts your appliance uses, then multiply by hours per day and cost per kWh to estimate your monthly charge.

💡 Examples

Below are common real-world examples using the DC Power Calculator:

Scenario	Known Values	Calculated
LED bulb at 12V, 0.5A	V=12V, I=0.5A	P=6W, R=24Ω
Car battery 12V, 60W	V=12V, P=60W	I=5A, R=2.4Ω
Heater 220V, 1000W	V=220V, P=1000W	I=4.55A, R=48.4Ω
Fan motor 5A, 100Ω	I=5A, R=100Ω	V=500V, P=2500W
Phone charger 5V, 10W	V=5V, P=10W	I=2A, R=2.5Ω

For AC circuits example: A single-phase load with V=230V (θv=0°) and I=10A (θi=−30°) gives φ=30°, Real Power P=1993W, Reactive Power Q=1150VAR, Power Factor=0.866.

❓ Frequently Asked Questions (FAQ)

What is the difference between DC and AC power?

DC (Direct Current) flows in one direction and is used in batteries, electronics, and solar systems. AC (Alternating Current) reverses direction periodically and is used in home electricity supply. DC power uses simple V, I, R, P relationships; AC power also involves phase angles and complex power (S, P, Q).

How many values do I need to enter?

For the DC calculator, you need any 2 of the 4 values (Voltage, Current, Resistance, Power). For the AC calculator, you need 2 magnitudes plus 2 phase angles to calculate the complete power profile.

What is Power Factor (PF)?

Power Factor is the ratio of real power (watts) to apparent power (volt-amperes). A PF of 1.0 means 100% efficient power use. Low PF (e.g., 0.7) means more current is drawn than needed, which increases electricity costs. PF = |cos φ| where φ is the phase difference between voltage and current.

Can I use this calculator for 3-phase power?

This calculator is designed for single-phase DC and AC circuits. For 3-phase power, the total power is 3× the single-phase power (balanced loads), or you can calculate per-phase and multiply. A dedicated 3-phase calculator will be added soon on CheckBillOnline.com.

Why does the Calculate button stay grey?

The Calculate button activates (turns blue) only when you have entered enough values to solve the unknowns. For DC: you need at least 2 fields filled. For AC: you need at least voltage or current magnitudes plus both phase angles.

Is this calculator free to use?

Yes! CheckBillOnline.com provides this Power Calculator completely free of charge. No registration, no subscription, and no hidden fees. You can bookmark this page and use it anytime.

What units are supported?

The DC calculator supports volts/kilovolts/millivolts, amps/milliamps/kiloamps, ohms/kilohms/megaohms, and watts/kilowatts/milliwatts. The AC calculator supports volts/kilovolts, amps/milliamps, ohms/kilohms, and VA/kVA. All unit conversions are handled automatically.

How does this help me check my electricity bill?

Enter your appliance's voltage and current (from its label) to find its wattage. Then: Monthly kWh = Watts × Hours/day × 30 ÷ 1000. Multiply by your utility's rate per kWh to get the monthly cost for that appliance. This helps you identify energy-hungry devices.

CheckBillOnline.com Team

Electrical & Energy Calculation Specialists. We build free online tools to help consumers, engineers, and students understand electricity, bills, and power systems. All tools on CheckBillOnline.com are reviewed for accuracy and updated regularly. Questions? Contact us via our website.

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