Calculate electrical power using Ohm's Law: P = V × I, P = V²/R, or P = I² × R. Essential for electronics, appliances, and circuit design.
📊 Calculated Power
0 W
P = V × I = 220V × 2A = 440 Watts
⚡ Ohm's Law Power Formulas
P = V × I | P = V² / R | P = I² × R Also: 1 Kilowatt (kW) = 1000 Watts | 1 Horsepower (HP) = 746 Watts
📖 What is Electrical Power?
Electrical power is the rate at which electrical energy is transferred or consumed in a circuit. It is measured in Watts (W). One Watt equals one Joule per second. Understanding power is essential for sizing electrical components, calculating electricity bills, and designing safe circuits.
📐 Power Formulas (Ohm's Law)
P = V × I (Power = Voltage × Current) P = V² / R (Power = Voltage² ÷ Resistance) P = I² × R (Power = Current² × Resistance)
📊 Power Consumption of Common Appliances
Appliance
Typical Power (Watts)
Daily Usage (hrs)
Monthly Energy (kWh)
Monthly Cost (₹7/kWh)
LED Bulb (10W)
10 W
5 hrs
1.5 kWh
₹10.5
Ceiling Fan
75 W
8 hrs
18 kWh
₹126
Refrigerator
200 W
24 hrs
60 kWh
₹420
1.5 Ton AC
1800 W
6 hrs
324 kWh
₹2,268
Water Heater
2000 W
1 hr
60 kWh
₹420
Microwave Oven
1000 W
0.5 hr
15 kWh
₹105
Laptop Charger
65 W
4 hrs
7.8 kWh
₹54.6
Mobile Charger
10 W
3 hrs
0.9 kWh
₹6.3
💡 How to Calculate Electricity Bill from Power
Electricity bills are calculated in kilowatt-hours (kWh). One kWh is 1000 Watts used for 1 hour.
Energy (kWh) = Power (Watts) × Hours Used ÷ 1000
Bill Amount = Energy (kWh) × Rate per kWh (e.g., ₹7/kWh)
Example: A 100W bulb used for 5 hours daily: 100 × 5 × 30 = 15,000 Wh = 15 kWh monthly × ₹7 = ₹105 per month.
🔋 Power Unit Conversions
1 Kilowatt (kW) = 1000 Watts
1 Megawatt (MW) = 1,000,000 Watts
1 Horsepower (HP) = 746 Watts
1 kWh = 1 unit of electricity (as shown on electricity meter)
1 Watt-hour (Wh) = 1 Watt used for 1 hour
📝 How to Use This Power Calculator
Select the formula you want to use: P = V×I, P = V²/R, or P = I²×R
Enter the required values (Voltage & Current, Voltage & Resistance, or Current & Resistance)
Click preset buttons for quick common values
View the calculated power in Watts, Kilowatts, and Horsepower
Use the result to calculate electricity bills or select appropriate components
📝 Frequently Asked Questions (FAQ)
❓ What is electrical power? ▼
Electrical power is the rate at which electrical energy is consumed or produced. Measured in Watts (W), it indicates how much work can be done per second. One Watt equals one Joule per second. For example, a 100W bulb uses 100 Joules of energy every second.
❓ How do I calculate power using Ohm's Law? ▼
Power can be calculated three ways: P = V × I (voltage × current), P = V² / R (voltage squared ÷ resistance), or P = I² × R (current squared × resistance). All formulas give the same result and are derived from Ohm's Law.
❓ What is the difference between Watts, Kilowatts, and Horsepower? ▼
1 Kilowatt (kW) = 1000 Watts. 1 Horsepower (HP) = 746 Watts. Household electricity bills are measured in kilowatt-hours (kWh). 1 kWh = 1000 Watts used for 1 hour.
❓ How to calculate electricity bill from power? ▼
Energy (kWh) = Power (Watts) × Hours Used ÷ 1000. Bill Amount = Energy (kWh) × Rate per kWh (e.g., ₹7 per kWh). Example: 100W bulb × 5 hours × 30 days = 15 kWh × ₹7 = ₹105 per month.
❓ What is power factor and why does it matter? ▼
Power factor is the ratio of real power (Watts) to apparent power (VA). For AC circuits with motors, power factor < 1. Real Power = Voltage × Current × Power Factor. Industrial users pay penalties for low power factor. This calculator assumes power factor = 1 (DC or resistive loads).
❓ What is the difference between AC and DC power calculation? ▼
For DC and resistive AC loads (like heaters, incandescent bulbs), P = V × I works directly. For inductive AC loads (motors, transformers, fans), use P = V × I × Power Factor. This calculator assumes DC or resistive AC loads (power factor = 1).
💡 Educational Note: The Watt (W) is named after Scottish inventor James Watt (1736-1819), who improved the steam engine. One Watt is defined as one Joule per second. Understanding power helps you calculate electricity costs, choose energy-efficient appliances, and design safe electrical circuits.