Electrical Technician Resource

Electrical Service
Calculators.

Field-friendly calculations for controls, transformers, motors, three-phase systems, analog signals, coils and resistor identification.

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Power & Load Calculations

Electrical Fundamentals, Transformers & Motors.

Calculated values are intended for troubleshooting and preliminary review. Use equipment nameplates, manufacturer data and applicable electrical requirements for final selections.

Ohm's Law

Select the two known values to calculate voltage, current, resistance and power.

Voltage—
Current—
Resistance—
Power—

Single & Three-Phase Power

Calculate apparent power, real input power and estimated delivered output.

Apparent Power—
Real Input Power—
Estimated Output—
Estimated Output—

Transformer kVA & Current

Calculate required transformer capacity from secondary load current and compare primary and secondary full-load current.

Calculated Capacity—
Primary Current—
Secondary Current—
Voltage Ratio—

Motor HP, kW & Current

Convert motor output rating and estimate input power and current using voltage, phase, efficiency and power factor.

Output Horsepower—
Output Kilowatts—
Estimated Input—
Estimated Current—

Motor & Control Diagnostics

Three-Phase, Signal and Circuit Checks.

Quick calculations for measurements commonly taken at motors, transformers, control cabinets, sensors, valves and analog devices.

Three-Phase Imbalance

Calculate voltage and current imbalance from three measured phase values.

Average Voltage—
Voltage Imbalance—
Average Current—
Current Imbalance—

Motor Synchronous Speed

Calculate synchronous RPM and compare it with measured or nameplate speed.

Synchronous Speed—
Calculated Slip—

Analog Signal Scaling

Convert measured 4–20 mA, 0–10 V or ±10 V signals to engineering units and calculate the expected signal.

Scaled Measurement—
Expected Signal—

DC Voltage Drop

Estimate copper-conductor voltage drop using one-way cable length and the complete out-and-back circuit.

Voltage Drop—
Voltage at Load—
Percentage Drop—
Circuit Resistance—

Coil & Solenoid

Estimate coil current, wattage or expected resistance from the rated voltage and one known value.

Expected Current—
Expected Resistance—
Expected Wattage—
Measurement ReminderCalculated motor current and voltage-drop values are estimates. Confirm motor current against the nameplate and manufacturer data. De-energize equipment and follow the required electrical safe-work procedure before resistance or continuity testing.

Component Identification

Resistor Identification & Circuit Tools.

Decode color bands and SMD markings, reverse-build a color code, calculate series or parallel resistance and check resistor power dissipation.

Identified resistance—Select the resistor bands.

Reverse Color Lookup

Enter a resistance and tolerance to display the nearest representable 4- or 5-band code.

SMD Marking Decoder

Decode common 3-digit, 4-digit, R-decimal and EIA-96 resistor markings.

Decoded Value—

Series & Parallel Resistance

Enter resistor values separated by commas. Use one unit for the entire list.

Series Total—
Parallel Total—

Resistor Power Dissipation

Calculate actual resistor dissipation using applied voltage or circuit current.

Power Dissipation—
Circuit Current—

Nearest Standard Value

Find the closest common E12, E24 or E96 resistance value.

Nearest Standard Value—
Resistor Testing ReminderDisconnect power and discharge stored energy before resistance measurements. In-circuit readings can be affected by parallel components; lift one resistor lead when necessary. Replace damaged or heat-discolored components only after identifying and correcting the cause of failure.