The Electricity Calculator collection covers the core formulas every electronics enthusiast, student, and technician needs. Solve circuit fundamentals with Ohm's Law Calculator, size wiring runs with the Voltage Drop Calculator, find combined resistance with the Resistors in Series and Parallel Resistor calculators, and select the right current-limiting component with the LED Light Resistor Calculator.
Check the Popular list to jump straight to the most-used tools, or visit the Trending tab to discover what builders are working on. All calculators are free, need no sign-up, and run on any device.
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Resistivity CalculatorCalculate the electrical resistance of a wire from its resistivity, length, and cross-sectional area using R = ρL/A. Free, instant, accurate.
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Capacitive Voltage Divider CalculatorCalculate the output voltage of a resistive voltage divider using Vout = Vin × R2 / (R1 + R2). Also gives divider ratio, current and power.
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Running Amps and Startup Load CalculatorSize a generator by adding running watts plus the largest startup surge. Enter your appliances to find the minimum wattage and a recommended size.
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VinFast Charge Time from Amps CalculatorEstimate VinFast EV charging time from charger power (kW), battery capacity, and start/target charge percent. Quick, simple hours and minutes estimate.
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Voltage Divider CalculatorCalculate the output voltage of a resistive voltage divider from Vin, R1 and R2. Also finds loop current and total power dissipated.
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Wire Resistance CalculatorCalculate the electrical resistance of a wire from its resistivity, length, and cross-sectional area using R = ρL/A. Free online tool.
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EV Cost Per Mile CalculatorCalculate the energy cost per mile of your electric vehicle from its efficiency (miles/kWh) and your electricity rate. See cost per 100 miles and trip cost.
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kVA to kW CalculatorConvert apparent power (kVA) to real power (kW) using the power factor. Free kVA to kW calculator with reactive power (kVAR) output.
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Wire Gauge (AWG) CalculatorConvert American Wire Gauge (AWG) to conductor diameter and cross-sectional area, and estimate copper wire current capacity (ampacity) by density.
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Home Solar Panel CalculatorEstimate how many solar panels and what system size (kW) you need based on your monthly electricity use, peak sun hours, panel wattage and efficiency.
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Voltage Drop Calculator (mm²)Calculate cable voltage drop in volts and percent for single-phase and three-phase copper or aluminium conductors sized in mm², by current and length.
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3 Phase Voltage Drop CalculatorCalculate three-phase voltage drop from load current, cable length, conductor resistivity, cross-section and power factor. Get volts dropped and percentage.
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18650 Battery Pack CalculatorCalculate the voltage, capacity (Ah), total cell count and energy (Wh) of an 18650 battery pack from any series-parallel (SxP) configuration.
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DC Voltage Drop CalculatorCalculate DC voltage drop across wire from current, length, and resistance. Get volts dropped, drop percentage, and voltage at the load instantly.
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Hydropower Output CalculatorCalculate hydroelectric power output from water flow rate, head, and efficiency using P = ρgQHη. Results in watts and kilowatts.
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Watt's Law CalculatorFree Watt's Law calculator. Solve for power (P), voltage (V), or current (I) using P = V × I. Enter any two values to find the third instantly.
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Electricity Units to kWh CalculatorConvert electricity units to kilowatt-hours (1 unit = 1 kWh) and estimate your bill cost from units consumed and your per-unit tariff.
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Monthly Electricity Cost from Watts CalculatorCalculate the monthly electricity cost of any device from its wattage, daily usage hours and your per-kWh rate. Get daily, monthly and yearly estimates.
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Motor Torque from kW and RPM CalculatorCalculate electric motor torque in newton-metres from power (kW) and speed (RPM) using T = 9549 x kW / RPM. Includes lb-ft conversion.
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Battery Discharge Time CalculatorEstimate how long a battery will last from its amp-hour capacity, load current, and usable depth of discharge. Free runtime calculator: t = (Ah × DoD) / A.
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kWh from Amps, Volts and Hours CalculatorCalculate electricity usage in kWh from amps, volts and hours. Enter current, voltage and run time to get energy used, power in watts and cost.
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Electricity Bill CalculatorEstimate your electricity bill from units consumed (kWh), the per-unit rate, and any fixed charge. Free, fast, and works with any currency.
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Power from Torque and RPM CalculatorCalculate mechanical power in kW, watts and horsepower from torque (N·m) and rotational speed (RPM) using P = T × RPM / 9549.
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EV vs Gas Cost per Mile CalculatorCompare the cost per mile of driving an electric vehicle versus a gas car. Enter kWh/mile, electricity price, gas price, and MPG to see your savings.
Frequently asked questions
What electrical calculations can I do here?
You can apply Ohm's Law to find voltage, current, or resistance; calculate total resistance for series and parallel networks; determine safe voltage drop across a wire run; find the right resistor for an LED circuit; and decode resistor color bands instantly with the Resistor Color Code Calculator.
Are these calculators free?
Yes — completely free, no account needed, and nothing to install. Open any tool on a phone, tablet, or computer and get your answer right away.
How accurate are the results?
The tools use well-established electrical engineering formulas including Ohm's Law, Kirchhoff's voltage law, and standard voltage-drop equations. Results are suitable for educational use and prototype planning. For installations governed by safety codes, always verify your calculations against the applicable electrical standard such as NEC or IEC 60364 and have a qualified electrician or engineer review the design.
Are my circuit values saved?
No. Every calculation runs locally in your browser. The resistances, voltages, and currents you enter are never stored on our servers or transmitted anywhere.
Which electrical calculators are most popular?
The Popular list is sorted by real user traffic, with the most-used tools at the top. You can also browse Trending for fast-moving picks, Recently Added for the newest calculators, or Last Updated for recently revised entries.
