Electrical & Engineering Calculators
Circuit and shop-floor math for makers, electricians and engineering students. Decode resistors, size wire for voltage drop, convert watts, amps and kVA, and work out gear ratios and beam loads.
20 calculators
Most used
- Resistor Color Code CalculatorTurn resistor color bands into a resistance with tolerance, or look up the bands for a value you need — with a drawing of the resistor.
- Voltage Drop CalculatorEstimate the voltage lost along a wire run, the voltage left at the load and the smallest copper or aluminum size that keeps the drop under 3%.
- Watts to Amps CalculatorTurn a wattage into current for DC, single-phase or three-phase power, with power factor, motor efficiency and the 125% figure used for continuous loads.
- Wire Gauge (AWG)Look up the diameter, cross-section, resistance and weight of any AWG size in copper or aluminum, or convert a metric size or measured wire to AWG.
Circuits & components 7
- Capacitor CalculatorTotal up capacitors in series or parallel, work out charge and stored energy, or read the three-digit code printed on a ceramic capacitor.
- LED Resistor CalculatorWork out the series resistor an LED needs from the supply voltage, LED color and current, then round to a standard value you can actually buy.
- RC Time Constant CalculatorGet τ = RC for any resistor and capacitor, plot the charge or discharge curve, and find the voltage at a time or the time to reach a voltage.
- Reactance & ResonanceFind XL and XC at a frequency, the resonant frequency of an inductor and capacitor, series RLC impedance and Q, or the part needed to tune a circuit.
- Resistor Color Code CalculatorTurn resistor color bands into a resistance with tolerance, or look up the bands for a value you need — with a drawing of the resistor.
- Series & Parallel ResistorsPaste a list of resistor values to get the series and parallel totals, the current and power in each one, and the resistor to add for a target.
- Voltage Divider CalculatorFind the output of a two-resistor divider, or the resistor that gives the voltage you need, including loading and standard-value suggestions.
Power & wiring 9
- Amps to Watts CalculatorMultiply current by voltage the right way for DC, single-phase or three-phase power, and see how many watts a circuit can safely carry continuously.
- Battery Life CalculatorEstimate battery runtime from capacity and load — current, power through an inverter, or a sleep/active duty cycle — with a realistic usable-capacity allowance.
- kVA CalculatorConvert between kVA and amps for single-phase or three-phase power, with real power in kW and the next standard transformer rating.
- Power Factor CalculatorMeasure power factor from kW, volts and amps, or size the capacitor bank in kVAR and microfarads to raise it to a target such as 0.95.
- Solar Panel CalculatorSize a solar array from your electricity use and local sun hours: system kW, number of panels, yearly production, roof area and a simple payback.
- Three-Phase Power CalculatorWork out kW, kVA and kVAR for a balanced three-phase load, or the line current for a given power, with per-phase values for wye and delta.
- Voltage Drop CalculatorEstimate the voltage lost along a wire run, the voltage left at the load and the smallest copper or aluminum size that keeps the drop under 3%.
- Watts to Amps CalculatorTurn a wattage into current for DC, single-phase or three-phase power, with power factor, motor efficiency and the 125% figure used for continuous loads.
- Wire Gauge (AWG)Look up the diameter, cross-section, resistance and weight of any AWG size in copper or aluminum, or convert a metric size or measured wire to AWG.
Mechanical 4
- Beam Deflection CalculatorFind how far a simply supported or cantilever beam sags under a point or uniform load, with moment, shear, reactions, stress and an L/360 check.
- Gear Ratio CalculatorFind the ratio of a gear pair or compound train from tooth counts, plus the output speed, output torque after friction losses and which way it turns.
- Stress, Strain & Young's ModulusFind stress, strain and Young's modulus from a load test, or predict how much a bar stretches under an axial load, with a yield-strength check.
- Torque CalculatorWork out torque from a force on a lever, the force or wrench length a torque spec needs, or the link between torque, horsepower and rpm.