Electricity Calculator
Compute electrical power (W), resistance (Ω), energy (kWh), and running cost from voltage & current. Free calculator with charts for India, US, and UK.
About This Calculator
The Electricity Calculator helps you compute electrical power, resistance, energy consumption, and operating cost for any electrical device or appliance. Simply enter the voltage and current ratings of your device — the calculator uses Ohm's Law and the electrical power formula to instantly compute all key electrical parameters. You can optionally add daily usage hours and your local electricity rate to estimate energy consumption in kilowatt-hours and daily operating cost.
The calculator applies three fundamental electrical formulas: Power (P) = Voltage (V) × Current (I) to compute wattage, Resistance (R) = Voltage (V) ÷ Current (I) via Ohm's Law, and Energy (E) = Power (P) × Time (t) ÷ 1000 to determine kilowatt-hour consumption. For example, a refrigerator running on 230V drawing 1.5A has a power rating of 345W and a resistance of 153Ω. If operated 8 hours daily at ₹8/kWh, it consumes 2.76 kWh per day costing approximately ₹22 per day.
The results section displays power in watts, resistance in ohms, voltage, and current. When usage details are provided, additional results show daily energy consumption in kilowatt-hours and estimated daily cost. The comparison chart visualizes the four electrical parameters side by side, while the breakdown chart shows energy and cost distribution when usage data is available.
Regional Notes
India: Standard household voltage is 230V at 50Hz. Electricity rates range from ₹6–₹10/kWh depending on state and slab, with a national average around ₹8/kWh. Many states offer subsidized rates for lower consumption brackets. The default voltage of 230V and rate of ₹8/kWh reflect typical Indian household conditions.
US: Standard household voltage is 120V at 60Hz. Average residential rates are ~$0.14/kWh (2025), varying from $0.11/kWh (Louisiana, Oklahoma) to $0.44/kWh (Hawaii). The default voltage of 120V and rate of $0.14/kWh reflect typical US conditions.
UK: Standard household voltage is 230V at 50Hz. Average rates are ~£0.28/kWh under the Energy Price Guarantee. Standing charges add a fixed daily cost. Economy 7 tariffs offer cheaper overnight rates. The default voltage of 230V and rate of £0.28/kWh reflect typical UK conditions.
Frequently Asked Questions
How is electrical power calculated from voltage and current?
Electrical power is calculated using the formula P = V × I, where P is power in watts, V is voltage in volts, and I is current in amperes. For example, a device running on 230V drawing 5A consumes 230 × 5 = 1,150 watts or 1.15 kW.
How do I calculate electrical resistance using Ohm's Law?
Resistance is calculated using Ohm's Law: R = V ÷ I, where R is resistance in ohms (Ω), V is voltage in volts, and I is current in amperes. For example, if a 230V device draws 5A, its resistance is 230 ÷ 5 = 46Ω.
How do I calculate energy consumption in kilowatt-hours?
Energy in kilowatt-hours is calculated as E = (P × t) ÷ 1000, where P is power in watts and t is time in hours. For example, a 1,150W device running 6 hours daily consumes (1,150 × 6) ÷ 1000 = 6.9 kWh per day.
What is the standard household voltage in different countries?
Standard household voltages vary by country: India, UK, Europe, Australia, and most of Asia use 220-240V at 50Hz. The US, Canada, Japan, and parts of South America use 100-127V at 60Hz. Always check your device's voltage rating before plugging it in.
What is the average electricity rate in India, US, and UK?
Average residential electricity rates as of 2025: India ranges from ₹6 to ₹10 per kWh depending on state and consumption slab (national average ~₹8/kWh). US averages ~$0.14/kWh varying by state from $0.11 to $0.44/kWh. UK averages ~£0.28/kWh under the Energy Price Guarantee with additional standing charges.
How can I reduce my appliance electricity costs?
To reduce electricity costs: replace old appliances with energy-efficient models (5-star BEE rated in India, Energy Star in US), use power strips to avoid standby consumption, run high-power appliances like AC and water heaters during off-peak hours, maintain appliances regularly, and switch to LED lighting which uses 80% less energy than incandescent bulbs.
What is the difference between watts, kilowatts, and kilowatt-hours?
Watts (W) measure instantaneous power — the rate of energy transfer. Kilowatts (kW) equal 1,000 watts. Kilowatt-hours (kWh) measure total energy consumed over time. For example, a 1kW appliance running for 1 hour consumes 1 kWh of energy. Your electricity bill charges for kWh consumed, not watts.
Is this electricity calculator free to use?
Yes, this electricity calculator on Calculy is completely free to use with no registration required. You can save results via shareable URL links and toggle between chart views to visualize electrical parameters and energy costs.