Electrical Calculators
Electrical calculators for quick field checks. Results are field calculations, not a substitute for manufacturer limits, meter verification, or electrical safety procedure.
Enter exactly two known values to calculate the remaining two.
Known Values
Enter exactly two values. Leave the two unknowns blank.
Advanced
Formula: V = I × R. P = V × I. Related forms are used depending on which two values are entered.
Assumptions: Ideal DC and simple resistive-circuit relationships.
Warnings: Measure resistance only on a de-energized circuit. Motors, coils, transformers, and drives require additional electrical relationships.
Estimate real power from voltage, current, and power factor.
Electrical Readings
Use balanced three-phase line voltage and line current from the same operating condition.
Advanced
Formula: kW = volts × amps × 1.732 × power factor ÷ 1000.
Assumptions: Voltage and current are treated as balanced three-phase line values.
Warnings: If power factor is estimated instead of measured, calculated kW is also estimated.
Calculate percent imbalance from three phase-current readings.
Phase Current
Use all three phase-current readings from the same operating condition.
Advanced
Formula: % imbalance = maximum deviation from average ÷ average current × 100.
Assumptions: All three readings are taken under the same operating condition and are directly comparable.
Warnings: Verify readings with a calibrated meter and compare against equipment-manufacturer limits.
Calculate synchronous speed and estimate loaded shaft speed.
Motor and VFD
Use VFD output frequency and motor pole count. Nameplate RPM is optional.
Advanced
Formula: Synchronous RPM = 120 × frequency ÷ motor poles.
Assumptions: When nameplate RPM is entered, estimated loaded RPM scales nameplate full-load speed in proportion to frequency.
Warnings: Actual shaft RPM depends on motor load, slip, VFD control method, programmed limits, and driven-equipment conditions.
Calculate required VA or available secondary current.
Transformer Inputs
Choose the calculation mode, then enter secondary voltage and the known value.
Advanced
Formula: VA = volts × amps. Amps = VA ÷ volts.
Assumptions: This uses the basic single-phase volt-ampere relationship for transformer secondary loads.
Warnings: The result does not add sizing margin or account for inrush, duty cycle, simultaneous loads, fuse sizing, conductor sizing, or manufacturer requirements.