Electricity Calculator – Cost, kWh, Amps And Monthly Bill
This electricity calculator helps you understand how much energy your appliances use and how much they cost to run. You can calculate electricity cost for a single device, estimate current and power from voltage, convert between watts and kilowatt-hours, and build a simple multi-appliance bill estimate based on your daily usage.
Basic Electricity And Energy Formulas
Several simpleationships appear across all tabs on this page:
- Power: P = V × I (watts)
- Energy: E = P × t / 1000 (kWh when P is in watts and t in hours)
- Cost: Cost = kWh × Rate (per kWh)
- Current: I = P ÷ (V × PF)
Power is the rate at which a device uses energy, while energy is the total amount used over time. Your electricity bill is usually based on energy in kilowatt-hours and the tariff rate per kWh. The calculators on this page keep units consistent and show daily, monthly and yearly perspectives where useful.
Using The Electricity Cost And Appliance Tabs
The electricity cost tab starts from a known power rating. You enter the wattage or kilowatts, hours of use per day, number of days and your rate per kWh. The tool outputs energy in kWh, total cost for the period and approximate cost per day, month and year.
The appliance tab is useful when you know voltage and current rather than watts. It uses power factor to estimate real power, then calculates daily and monthly energy and optional cost. This helps you compare the effect of changing settings, usage time or replacing an older appliance with a more efficient model.
Amps, Watts And Voltage Tabs
The amps, watts and voltage tabs give quick one-line calculations for common electrical questions:
- Amps calculator – Find current from power and voltage so you can size cables or breakers.
- Watts calculator – Turn volts and amps into watts and apparent power for planning loads.
- Voltage calculator – See what supply voltage is implied by a given power and current.
These tabs are especially handy when you are checking labels on devices, working with extension cords or planning how many loads can safely share a branch circuit. For more detailed circuitationships, you can use the Ohm’s Law Calculator.
kW, kWh And Monthly Electric Bill
The converter tab connects power and energy with hours. For example, a 2 kW heater running for 3 hours uses:
Energy = 2 kW × 3 h = 6 kWh
The electric bill tab scales that idea across several appliances. You enter a few typical devices such as air conditioning, lighting and refrigeration, along with hours of use and your rate per kWh. The calculator estimates total monthly kWh and cost and shows a simple breakdown so you can see which loads dominate.
For projects that involve wiring runs or voltage drop over distance, you can pair this tool with a Voltage Drop Calculator, or with a Square Footage Calculator when you are planning lighting and outlet layouts by room size.
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Use these math and probability calculators to handle everyday calculations, homework, and quick checks.
Electricity Usage & Power Cost
Frequently Asked Questions
Get clear explanations electricity rates, watts vs amps vs kWh, bill estimation accuracy, and single-phase vs three-phase usage.
Most utility bills list a price per kWh. Enter that number in the rate fields. If your bill includes multiple pricing tiers or taxes, you may either approximate using an average rate or run separate calculations for each tier and combine the results.
Watts describe how powerful a device is at any moment, amps show how much current it draws, and kWh measure how much total energy it uses over time. Utility bills are based on kWh, but watts and amps help with cable sizing, breaker selection and safe circuit loading.
Accuracy depends on the inputs you provide. If your power ratings and hours of use are realistic, the estimated bill is usually close enough for planning and comparison. Actual utility charges may differ due to meter rounding, taxes, seasonal tariffs and other fees not included in this calculator.
This tool assumes single-phase loads using line-to-neutral voltage. This is sufficient for most homes and small offices. Larger three-phase systems require formulas specific to three-phase power, so use dedicated tools and consult a licensed electrician or engineer for detailed design work.