Electrical Engineering Calculators

Electrical Engineering Calculators - Circuit Design and Power Calculations

Electrical calculations are central to every electronics project, power system, and electrical installation. From decoding a resistor’s colour bands to sizing a solar array, these calculators cover the breadth of practical electrical engineering - referencing NEC, IEC, and AWG standards where relevant.

Twenty-Nine Electrical Engineering Calculators

Resistor Colour Code Calculator - Decodes 4-band and 5-band resistor values from colour band selection. Also works in reverse: enter a resistance value and get the correct colour band sequence. Uses the EIA standard colour code table.

Voltage Divider Calculator - V_out = V_in × R2 ÷ (R1 + R2). Enter any three values to find the fourth. Shows divider ratio and current draw. Used in sensor interfaces, ADC scaling, and BJT biasing. Pair with the Ohm’s Law Calculator for the full circuit picture.

Transformer Ratio Calculator - Three modes: find secondary voltage (V2 = V1 × N2/N1), find turns ratio for a required transformation, and find impedance transformation (Z2 = Z1 × (N2/N1)²). Used in power supply design, audio impedance matching, and mains isolation.

Wire Gauge Calculator - AWG lookup (diameter, area, resistance/metre, ampacity at 60/75/90°C insulation ratings) and voltage-drop calculation for any run length and current, with NEC 3% threshold warning.

Power Calculator - P = VI = I²R = V²/R. Enter any two of V, I, R, P to get the other two. The essential complement to the Ohm’s Law Calculator - use them together for complete circuit characterisation.

Solar Panel Output Calculator - Daily, monthly, and annual energy generation from panel capacity (Wp), peak sun hours, and system efficiency. Array sizing mode: enter daily consumption and PSH to find required panel capacity, battery storage (Ah), and estimated annual savings.

Flyback Converter Calculator - Two modes: Turns Ratio (N = Np/Ns = Vin x D / (Vout x (1-D))) finds the transformer turns ratio, reflected voltage, peak switch voltage, and recommended Vds rating; Inductance and Current finds minimum magnetising inductance (Lm) and primary current (peak, average, RMS) for DCM operation. Essential for SMPS and isolated power supply design. Pair with the Transformer Ratio Calculator for winding design.

Inductor Energy Storage Calculator - E = 0.5 x L x I squared. Two modes: Find Energy (inductance in uH and peak current in A gives stored energy in J, mJ, uJ, and peak flux linkage in Wb for core saturation checks); Find Current (enter target energy in uJ and inductance to calculate the required peak current). Essential for SMPS inductor selection, filter design, and pulsed power applications.

MOSFET Threshold Voltage Calculator - Square-law MOSFET model. Two modes: Find Drain Current (Vgs, Vth, Kp, Vds gives Id in mA with automatic region detection: cutoff/linear/saturation plus overdrive voltage Vov and minimum Vds for saturation); Find Required Vgs (target Id, Vth, Kp gives the gate voltage needed assuming saturation operation). Covers N-channel enhancement MOSFETs for circuit design and education.

Resistor Wattage Calculator - P = VI = V2/R = I2R. Three modes: Voltage and Current, Voltage and Resistance, Current and Resistance. Recommends the correct standard wattage rating using IPC-2221 50% derating and consumer 67% derating, with auto-scaling output in mW or W.

RMS Voltage Calculator - Peak to RMS and RMS to Peak conversion for sine, square, triangle, and sawtooth waveforms. Shows V_peak, V_rms, V_pp, average voltage, crest factor, and form factor. Essential for power supply design and signal analysis.

Photon Detection Efficiency Calculator (SiPM) - PDE = QE times FF times Ptrig. Two modes: Find PDE (quantum efficiency, fill factor, and trigger probability give overall PDE with detected photons per 1000 incident and loss fraction); Signal Estimation (PDE, incident rate in kHz, DCR, and integration window in ns give SNR, signal counts, dark counts, and contrast ratio). Covers SiPM and SPAD detector design for medical imaging, LiDAR, and photon counting.

RLC Series Circuit Impedance Calculator - Z = sqrt(R squared plus (X_L minus X_C) squared). Finds inductive reactance X_L, capacitive reactance X_C, total impedance Z, and phase angle for a series RLC circuit at any frequency, with an impedance-vs-frequency chart showing the resonance dip. Pair with the Resonant Frequency Calculator and Quality Factor Calculator for the full resonance picture.

Resonant Frequency Calculator (LC Circuit) - Thomson’s formula f0 = 1 / (2 pi sqrt(LC)). Three modes: Find f0 (from L and C), Find L (from target f0 and C), and Find C (from target f0 and L). Used in radio tuning circuits, oscillators, and filter design.

Quality Factor Calculator - Q = (1/R) times sqrt(L/C) for a series RLC circuit. Also finds resonant frequency, bandwidth, and both half-power (3 dB) frequencies bracketing resonance. Use the same R, L, C values as the RLC Series Circuit Impedance Calculator to see how Q relates to the sharpness of that calculator’s impedance dip.

RLC Parallel Circuit Impedance Calculator - |Z| = 1 / sqrt((1/R) squared plus (omega C minus 1/(omega L)) squared). Finds total impedance, phase angle, resonant frequency, and quality factor Q = R sqrt(C/L) for a parallel RLC circuit, with an impedance-vs-frequency chart showing the resonance peak (opposite the series circuit’s resonance dip).

Transmission Line Impedance Calculator (Coaxial) - Z0 = (60 / sqrt(er)) x ln(D/d). Finds the characteristic impedance, capacitance per unit length, and velocity factor of a coaxial cable from its conductor diameters and dielectric constant, with a Z0-versus-D/d-ratio chart.

Transmission Line Impedance Calculator (Microstrip) - Hammerstad-Jensen approximation for a PCB microstrip trace’s characteristic impedance Z0 and effective dielectric constant from trace width, substrate height, and dielectric constant, with a Z0-versus-W/h-ratio chart.

Reflection Coefficient and VSWR Calculator - Reflection coefficient, VSWR, return loss, and mismatch loss for a resistive load against a characteristic impedance, with a VSWR-versus-load-impedance chart marking the matched Z0 point.

S-Parameter to Z-Parameter Converter - Converts 2-port S-parameters (S11, S12, S21, S22, entered as magnitude and phase) to Z-parameters using full complex arithmetic and a chosen reference impedance Z0, with step-by-step working in rectangular form.

Link Budget Calculator - Received power, free-space path loss, and link margin (Pr = Pt + Gt + Gr - FSPL - Lother) for a radio link, with a received-power-versus-distance chart marking the receiver sensitivity floor.

Bessel Filter Group Delay Calculator - Natural (design) frequency needed for a maximally-flat Bessel filter to deliver a target group delay at DC, using the delay-normalized relationship tau0 = 1/omega0.

Active Low-Pass Filter (Sallen-Key) Calculator - Resistor and gain-setting feedback resistor values for an equal-component Sallen-Key active low-pass filter from your target cutoff frequency and Q factor, covering the common Butterworth case.

Power Factor and Reactive Power Calculator - Real, reactive, and apparent power from the AC power triangle (P = VIcos-phi, Q = VIsin-phi), with automatic leading/lagging load classification and a labeled power triangle diagram.

Three-Phase Power Calculator (Balanced Load) - Total real, reactive, and apparent power for a balanced three-phase load (P = sqrt(3)VLILcos-phi), with a star/delta toggle reporting equivalent phase voltage and current.

Unbalanced Three-Phase Load Calculator - Total power and neutral current for an unbalanced three-phase load from each phase’s own voltage, current, and angle, using full phasor addition for the neutral current.

Symmetrical Components Calculator - Zero, positive, and negative sequence components from three unbalanced phasors using Fortescue’s symmetrical component transform, works for either voltage or current.

Skin Effect Depth Calculator - Skin depth from resistivity, relative permeability, and frequency, with an optional AC/DC resistance ratio estimate and an automatic validity check on that approximation.

Transformer Efficiency and Regulation Calculator - Efficiency at any load fraction, percent voltage regulation for lagging or leading power factor, and the load fraction giving maximum efficiency, with the efficiency-versus-load curve plotted.

For antenna gain, aperture, and radiation resistance calculators, see the Antenna Design subcategory.

Practical Reference: Solar in India

India receives 4–7 peak sun hours daily (PSH) - Rajasthan/Gujarat at 5.5–7, northeastern states at 3.5–4.5. A 1 kWp system at 5 PSH with 80% efficiency generates ~4 kWh/day = 1,460 kWh/year. At ₹7/kWh savings ≈ ₹10,220/year. Use the Solar Panel Output Calculator with your local PSH for accurate sizing.