Free, easy-to-use electrical calculators for wire thickness, voltage loss, electricity bills, circuit breaker safety, and component values. Instant step-by-step math based on National Electrical Code (NEC) guidelines.
Calculate wire size, breaker loads, electricity bills, and LED resistors instantly.
Browse our complete catalog of 23 free electrical and power calculators.
Find the safest American Wire Gauge (AWG) thickness for copper and aluminum conductors based on amps and continuous load.
Circular Mils = (2 × K × I × L) / Max Allowable Voltage DropCalculate Calculate voltage lost over long wire distances to prevent motor overheating and ensure NEC 3% compliance.
1-Phase: VD = (2 × K × I × L) / CM ; 3-Phase: VD = (√3 × K × I × L) / CMCalculate Calculate how many wires can safely fit into EMT, PVC, IMC, or Rigid conduit without exceeding 40% fill limits.
Conduit Fill % = (Total Area of All Conductors / Total Internal Area of Conduit) × 100%Calculate Calculate total volume allowances for conductors, clamps, switches, receptacles, and grounding wires in junction boxes.
Total Volume Required = Σ (Conductor Equivalents × Volume Allowance per Gauge in cu in)Calculate Size 15A, 20A, 30A, 50A breakers and verify that continuous loads running for 3+ hours do not exceed 80% capacity.
Minimum Breaker Rating = (Continuous Load Amps × 1.25) + Non-Continuous Load AmpsCalculate Calculate Voltage (Volts), Current (Amps), Resistance (Ohms), and Power (Watts) instantly from any two known values.
V = I × R ; P = V × I = I² × R = V² / RCalculate Calculate total equivalent resistance for any number of resistors connected in series or parallel branches.
Series: R_total = R₁ + R₂ + ... ; Parallel: 1/R_total = 1/R₁ + 1/R₂ + ...Calculate Calculate the exact resistor ohms and minimum wattage required to safely power single or multiple LEDs without burnout.
Resistor (Ω) = (Supply Voltage - LED Forward Voltage) / Desired LED Current (A)Calculate Convert between Root Mean Square (RMS) voltage, peak voltage ($V_{pk}$), and peak-to-peak voltage ($V_{pp}$) for sine waves.
V_RMS = V_Peak / √2 ≈ 0.7071 × V_Peak ; V_Peak-to-Peak = 2 × V_PeakCalculate Calculate power factor, active power (kW), reactive power (kVAR), and total apparent power (kVA) in AC electrical systems.
Power Factor (PF) = Real Power (kW) / Apparent Power (kVA) = cos(θ)Calculate Calculate electrostatic attraction or repulsion force between two point charges separated by a known distance.
F = k_e × (|q₁ × q₂|) / r² (where k_e ≈ 8.98755 × 10⁹ N·m²/C²)Calculate Calculate how much any appliance costs to run per hour, per day, per month, and per year based on your local kWh rate.
Cost = (Appliance Watts × Hours Used / 1,000) × Electricity Rate ($/kWh)Calculate Compare electricity consumption across air conditioners, space heaters, refrigerators, computers, and water heaters.
Monthly kWh = (Watts × Daily Hours × 30) / 1,000Calculate Calculate annual cost savings and payback time when upgrading incandescent or fluorescent bulbs to high-efficiency LEDs.
Annual Savings = [((Watts_Old - Watts_LED) × Hours/Day × 365) / 1,000] × Rate/kWhCalculate Calculate how many solar panels and how much battery storage (kWh / Ah) you need for off-grid or home backup power.
Battery Storage (Ah) = (Daily Wh × Days of Autonomy) / (Battery Voltage × Depth of Discharge)Calculate Calculate starting (surge) watts and running (continuous) watts needed to power your critical household appliances during an outage.
Generator Size (Watts) = Highest Starting Surge Watts + Total Running Watts of All LoadsCalculate Calculate capacitance in farads/microfarads, parallel plate dimensions, and total energy stored in a charged capacitor.
C = (ε_r × ε_0 × Area) / Distance ; Stored Energy E = ½ × C × V²Calculate Calculate single-layer air core coil inductance in microhenries (µH) and energy stored in an inductor ($E = ½LI^2$).
L (µH) = (d² × n²) / (18d + 40l) (Wheeler’s Formula for Air-Core Coils)Calculate Decode resistor color bands to find resistance in ohms, tolerance percentage, and temperature coefficient (ppm/K).
Resistance = (Band 1 & 2 digits) × 10^(Multiplier Band) ± Tolerance %Calculate Calculate resistance values from 3-digit, 4-digit, and EIA-96 precision surface-mount resistor codes.
3-Digit: AB × 10^C ; 4-Digit: ABC × 10^D ; EIA-96: Value Code Lookup × 10^Multiplier CodeCalculate Instantly convert Amperes (Current) to Watts (Power), Kilowatts (kW), and Volts across DC, 1-Phase AC, and 3-Phase AC.
Watts = Amps × Volts × Power Factor (1-Phase AC) ; Watts = √3 × Amps × Volts × PF (3-Phase AC)Calculate Convert electric motor mechanical horsepower (HP) to electrical kilowatts (kW) and calculate full load amps.
1 Mechanical HP = 0.74569987 kW ; kW = HP × 0.7457 ; HP = kW / 0.7457Calculate Convert decibel-milliwatts (dBm) to milliwatts (mW) and Watts (W) for audio, radio frequency (RF), and Wi-Fi signals.
Power (mW) = 10^(dBm / 10) ; Power (Watts) = 10^((dBm - 30) / 10)Calculate Pick your practical goal below to jump straight to the easiest calculator.
Check voltage loss over 50–500 ft runs to sheds, garages, or outdoor pumps.
Convert watts to amps and verify the 80% continuous safety limit.
Calculate the exact cost of running space heaters, AC units, and electronics.
Clear formulas, practical examples, and common wiring mistakes to avoid.
Voltage Lost = (2 × 12.9 × Amps × Distance in Feet) / Circular Mils AreaKeeping voltage loss under 3% ensures motors start smoothly and prevents wires from heating up.
Calculation: (2 × 12.9 × 16 × 100) / 6,530 = 6.32V lost (5.27% drop).
Power (Watts) = Voltage (Volts) × Current (Amps)Watts measures total electrical power, Volts is electrical pressure, and Amps is the rate of flow.
Calculation: 1,500 Watts ÷ 120 Volts = 12.5 Amps.
Clear answers to common questions about using our electrical calculators and safety guidelines.
Standard electrical safety guidelines recommend keeping voltage drop on any branch circuit under 3%. If voltage drops too much over long distances, electric motors run hot and burn out faster, lights dim, and battery chargers take much longer.
For appliances that run continuously for 3 hours or more (such as space heaters, EV chargers, or servers), electrical safety standards require sizing the circuit at 125% of the load. This ensures the breaker stays at or below 80% capacity to avoid nuisance trips from internal heat buildup.
Copper conducts electricity more easily and has lower resistance than aluminum, meaning you can use a thinner copper wire for the same electrical load. Aluminum is lighter and less expensive for large service entrance cables, but requires a thicker gauge.
Divide Watts by Volts. For example, a 1,200W hair dryer plugged into a standard 120V outlet draws: 1,200 ÷ 120 = 10 Amps.
120V is standard for everyday household wall plugs (lamps, TVs, laptops). 240V is used for high-power home appliances like electric dryers, ovens, water heaters, and EV chargers. 3-Phase power is used in commercial buildings and factories for heavy industrial machinery.
No. Our calculators provide accurate mathematical formulas and reference guidelines for planning your projects. For physical installations, panel upgrades, and permitted work, always consult your local municipal codes and a licensed electrician.
SolveItCalculator uses standard formulas from the National Electrical Code (NEC / NFPA 70), IEEE recommendations, and NIST reference constants so you can plan projects safely.
National Electrical Code (NEC 2023 edition), IEEE Standard 141 (Red Book), Ohm’s Law, and standard conductor resistivity formulas ($K = 12.9$ for copper, $K = 21.2$ for aluminum).
These calculators are designed for planning, estimation, and educational purposes. For final installations, permitted work, and main panel upgrades, always comply with local municipal building codes and hire a licensed master electrician.