Electrical Calculator

How to Use the Electrical Calculator

Select a mode, enter its values, and click Calculate. The result area shows the available steps, assumptions, and any warnings for that calculation.

Choose a mode from Calculation mode.
Enter the requested values and choose available units, material, or circuit type.
Click Calculate.
Review the result, Formula & steps, Assumptions, and any applicable warnings.
Use Copy result or Download result (.txt) to save the output.

Supported Calculation Modes

Watts / volts / amps / resistance (Ohm's law): enter exactly two of the four values.
Resistor combinations: choose Series or Parallel and enter at least two comma-separated values.
Voltage drop: enter current, one-way length, length unit, conductor material, wire gauge, conductor temperature, circuit type, and supply voltage.
Wire-size estimate: enter the circuit details and Max allowed voltage drop (%); the search covers AWG 18 through 4/0.
Battery runtime: enter capacity, load, efficiency, and voltage when the selected units require it.
Battery-bank sizing: enter daily energy need, autonomy, system voltage, depth of discharge, and individual battery capacity and voltage.
Energy consumption: enter power, hours used per day, number of days, and an optional electricity rate per kWh.

The Formulas Used

Ohm's law and power: V = I × R and P = V × I = I²R = V²/R. Enter exactly two of watts, volts, amps, or resistance.
Resistor combinations: series R_total = R1 + R2 + ...; parallel 1/R_total = 1/R1 + 1/R2 + ....
Voltage drop: the calculator uses conductor resistance, current, and a round-trip factor for DC/single-phase or √3 for three-phase.
Wire-size estimate: solves the voltage-drop formula for the maximum allowable resistance per length, then picks the smallest AWG size whose computed resistance is at or below that limit.
Battery runtime: usable watt-hours after the entered efficiency are divided by load watts.
Battery-bank sizing: daily energy, autonomy, depth of discharge, system voltage, and battery specifications determine the required capacity and arrangement. The tool rounds up to whole batteries.
Energy consumption: kWh = power (kW) × hours, with cost = kWh × rate when a rate is supplied.

How Conductor Resistance Is Calculated

Voltage-drop and wire-size resistance use the AWG diameter formula, copper or aluminum bulk resistivity, and the conductor temperature you enter. The result reflects the formula and solid-conductor geometry, not a specific manufacturer's stranded-wire data sheet.

Conductor-Temperature & Length Assumptions

Conductor temperature: the default is 75°C; resistance is adjusted from the 20°C reference using the material's temperature coefficient. Actual temperature can differ under load.
Length: enter the one-way distance. The calculator applies ×2 for DC and single-phase circuits, or √3 for three-phase circuits.
Load type: voltage drop and Ohm's law assume a resistive, unity-power-factor load; reactive loads (motors, most electronics) are not modeled.

Warnings and Unsupported Cases

Voltage-drop mode warns above 5% and states that ampacity is not checked.
Wire-size mode warns when no AWG size through 4/0 meets the target. kcmil sizes and parallel runs are unsupported.
Battery-bank sizing warns when the rounded-up series arrangement does not exactly match the requested system voltage. It does not model temperature derating, C-rate limits, battery aging or capacity fade, inverter or charge-controller efficiency, or manufacturer-specific DoD recommendations.
The calculator does not apply NEC, CEC, IEC, or another local code, and does not check ampacity, breaker/fuse sizing, grounding, or installation safety.

Input Validation

Numeric fields must contain finite numbers. Fields requiring positive values reject zero and negative entries. Ohm's law requires exactly two populated inputs, resistor combinations require at least two comma-separated values, and efficiency and depth-of-discharge inputs must be between 1 and 100.

What the Results Show

After calculation, the result can include statistics, Formula & steps, Assumptions, and warnings. Voltage-drop results show volts and percent. Wire-size results identify the smallest supported size that meets the target when one is found. Battery runtime shows hours and a day conversion; battery-bank sizing shows required capacity and a series/parallel arrangement. Energy consumption shows daily and total kWh, with estimated cost when you enter a rate. Warnings appear only for relevant cases and modes.

What This Tool Does Not Do

This calculator does not certify any electrical installation as safe or code-compliant. It does not apply the NEC, CEC, IEC, or any other local electrical code automatically, does not check conductor ampacity, breaker/fuse sizing, grounding, or arc-flash considerations, and does not account for reactive loads, harmonics, or three-phase unbalance beyond the simplified √3 length factor. It is not a substitute for a licensed electrician, and it does not provide professional engineering sign-off for real electrical work.

Privacy of Calculator Inputs

The calculator script performs calculations locally in your browser and contains no request for calculation inputs. This statement applies to calculator values; the page also has a separate subscription form.

Frequently Asked Questions

What electrical calculations does this tool support?

Seven modes: Ohm's law & power (watts, volts, amps, resistance), resistor combinations (series and parallel), voltage drop, wire-size estimate, battery runtime, battery-bank sizing, and energy consumption. Pick a mode from the dropdown and enter the requested values.

How does the voltage drop and wire size calculation work?

It computes conductor resistance from the standard AWG diameter formula and the bulk resistivity of copper or aluminum, adjusted for the conductor temperature you choose, then multiplies by current and the round-trip (or square root of 3 for three-phase) length factor. Wire-size mode searches standard AWG sizes 18 through 4/0 for the smallest one that keeps the drop under your target percentage.

Does this tool check wire ampacity or apply an electrical code?

No. It only estimates voltage drop, not ampacity (current-carrying capacity), which depends on insulation type, conduit fill, ambient temperature, and bundling under whatever electrical code applies in your jurisdiction (such as the NEC, CEC, or IEC). This tool does not apply any specific code automatically and does not certify an installation - verify ampacity and code compliance separately, and consult a licensed electrician for real installations.

Is this a substitute for a licensed electrician?

No. This tool performs deterministic arithmetic on the values you enter and states its formulas and assumptions transparently, but it does not inspect real wiring, does not know your local code requirements, and does not certify any installation as safe or compliant. Always consult a licensed electrician for actual electrical work.

What assumptions affect battery runtime and battery-bank sizing?

Battery runtime assumes a constant load power and discharge voltage, with the entered efficiency applied to usable watt-hours. Battery-bank sizing uses daily energy, autonomy, depth of discharge, system voltage, and the individual battery specifications; it rounds up to whole batteries. It does not model temperature derating, C-rate limits, aging, inverter or charge-controller efficiency, or manufacturer-specific DoD recommendations.

Result

Formula & steps

Assumptions