Electrical Calculators
Capacitor Calculator
Calculate capacitance, stored charge, stored energy, and RC time constant. Includes series and parallel capacitor combinations. Free capacitor calculator.
Electrical Load Calculator
Calculate your home electrical panel load. Add circuits by amps or watts to find total load, demand factor, and whether your panel is large enough. Free electrical load calculator.
Electricity Cost Calculator
Calculate the electricity cost of any appliance. Enter wattage, hours of use, and your rate per kWh to get hourly, daily, monthly, and yearly costs. Free electricity cost calculator.
LED Resistor Calculator
Calculate the correct resistor value for an LED. Enter supply voltage, LED forward voltage, and desired current to get the resistor value, nearest standard value, and wattage. Free LED resistor calculator.
Ohm's Law Calculator
Free Ohm's Law calculator. Enter any two values (V, I, R, or P) to instantly solve for the other two. Includes formulas, triangle diagram, and worked examples.
Power Factor Calculator
Calculate power factor, apparent power (kVA), real power (kW), and reactive power (kVAR). Single-phase and three-phase AC circuits. Free power factor calculator.
Resistor Calculator
Decode resistor color codes and calculate series and parallel resistance combinations. Supports 4-band and 5-band resistors. Free resistor calculator.
Voltage Drop Calculator
Calculate voltage drop over a wire run. Enter wire gauge, current, run length, and material to find voltage drop in volts and percent. Free voltage drop calculator.
Watts to Amps Calculator
Convert watts to amps or amps to watts for AC and DC circuits. Enter any two of watts, amps, or volts to calculate the third. Free watts to amps converter.
Wire Gauge Calculator
Find the correct wire gauge (AWG) for your electrical circuit. Enter current in amps and wire run length to get the minimum safe wire size. Free wire gauge calculator.
Electrical Calculators
Our 10+ free electrical calculators cover the most common calculations for homeowners, students, electricians, and electronics hobbyists — from Ohm's Law and wire sizing to electricity cost and LED resistors.
Ohm's Law and Basic Circuits
Almost every electrical calculation starts with Ohm's Law: V = I × R (voltage equals current times resistance). From this single relationship, you can derive the power formula P = V × I, and solve for any unknown in a DC circuit given two known values.
Wire Sizing and Voltage Drop
Choosing the correct wire gauge is one of the most safety-critical decisions in electrical work. Undersized wire overheats, creating a fire risk. Our wire gauge calculator recommends the minimum AWG for a given load and run length, while our voltage drop calculator shows how much voltage is lost over long wire runs.
Waste Factors and Safety Margins
| Application | Typical safety margin |
|---|---|
| Branch circuit breaker | Load no more than 80% of breaker rating |
| Service entrance / panel | Size at 125% of calculated load |
| Wire ampacity | Derate for conduit fill, temperature, and run length |
| Motor loads | Size wire at 125% of full-load current |
AC vs. DC Electricity
Most household circuits use alternating current (AC) at 120 V or 240 V (North America) or 230 V (Europe/Australia). Batteries and electronics use direct current (DC). Power formulas differ slightly — AC circuits have power factor to consider. Our calculators note where AC vs. DC matters.
Working Safely with Electricity
Always turn off the breaker and verify with a non-contact voltage tester before working on any circuit. For any work beyond replacing outlets and switches, consult a licensed electrician and obtain the required permits. These calculators are for estimation and educational purposes only and do not substitute for professional electrical advice.