⚡ Electronics & RF
Free electronics calculators: Ohm’s law, resistor codes, voltage drop, op-amp and filter design, LC resonance, antennas, RF links, decibels and 555 timer circuits.
Bench essentials in one place: Ohm’s law with power, four-band resistor color codes, standard E-series values, voltage drop over cable runs, and the 555 timer in its classic modes.
Design tools cover op-amp gain networks, Sallen-Key, Butterworth and Chebyshev filters, LC resonance, Zener regulation and Wheatstone bridges. RF side: link budget via Friis, radar range, path loss, antennas and power density.
555 Timer Calculator
Design 555 timer circuits in astable and monostable modes. Calculate frequency, duty cycle, pulse width from R1, R2, and C values, or find component values for a target frequency.
BJT Transistor Bias Calculator
Calculate the DC operating point (Q-point) of a BJT voltage divider bias circuit. Find collector current, collector-emitter voltage, base current, and stability margins.
Butterworth Filter Calculator
Calculate Butterworth filter component values (inductors and capacitors) for Tee and Pi, low-pass and high-pass configurations. Enter cutoff frequency and source/load impedance to get exact values.
Capacitor Energy Calculator
Calculate the energy stored in a capacitor, the charge it holds, and the RC time constant for charging/discharging through a resistor. Enter capacitance, voltage, and resistance.
Chebyshev Filter Calculator
Calculate Chebyshev filter component values (inductors and capacitors) for Tee and Pi, low-pass and high-pass configurations with 0.5 dB or 3 dB ripple. Enter cutoff frequency and impedance to get exact values.
Decibel Calculator
Convert between decibels (dB) and linear ratios for voltage and power. Calculate dBm, dBW, and signal gain/loss for audio, RF, and telecommunications applications.
Electrical Power Calculator
Calculate electrical power for DC and AC circuits. Compute real power (watts), apparent power (VA), reactive power (VAR), and power factor from voltage, current, and phase angle.
Friis Path Loss Calculator
Calculate free-space path loss and received power with the Friis transmission equation. Supports MHz or GHz, km or miles, and includes TX/RX antenna gain and cable loss.
Helical Antenna Calculator
Design axial-mode helical antennas for WiFi, 2.4 GHz and satellite downlinks. Compute circumference, pitch angle and theoretical gain from frequency, diameter, pitch and number of turns.
LC Resonance Calculator
Find the resonant frequency of an LC tank circuit from inductance and capacitance. Returns f₀ in Hz/kHz/MHz, characteristic impedance and Q factor with resistance.
Line of Sight Calculator
Calculate optical line of sight, radio horizon with 4/3 Earth factor, and 60% Fresnel zone clearance between two antenna heights. Essential for WiFi, microwave and Ham links.
Ohm's Law Calculator
Calculate voltage, current, resistance and power using Ohm's Law. Enter any two known values of V, I and R to instantly find the third, plus the power dissipated in the circuit.
Op-Amp Resistor Calculator
Design inverting and non-inverting op-amp amplifier circuits. Solve gain from resistor pairs, or find the feedback resistor needed for a target gain.
Parallel Plate Capacitor Calculator
Calculate the capacitance of a parallel plate capacitor from plate area, distance between plates, and dielectric material. Supports vacuum, air, paper, mica, ceramic, and polymer dielectrics.
Radar Range Equation Calculator
Estimate the maximum detection range of a radar from power, gain, wavelength, target radar cross-section and SNR. Returns range in km, miles and nautical miles.
Reactance Calculator
Calculate capacitive reactance Xc = 1/(2πfC) and inductive reactance XL = 2πfL from frequency and component value. Outputs in ohms, kΩ and MΩ with an LC resonance cross-check.
Resistor Color Code Calculator
Determine the resistance value, tolerance, and temperature coefficient of any resistor by selecting its color bands. Supports both 4-band standard resistors and 5-band precision resistors.
RF Power Density Calculator
Compute RF power density from EIRP and distance for safety and EMF exposure checks. Results in mW/cm², W/m² and µW/cm² with a comparison to common exposure limits.
RMS Value Calculator
Calculate the RMS (root mean square) value of AC waveforms. Convert between peak, peak-to-peak, and RMS for sine waves, square waves, triangle waves, and sawtooth waves.
Sallen-Key Filter Calculator
Calculate Sallen-Key active filter component values (capacitors and resistors) for unity-gain 2nd-order low-pass and high-pass configurations. Enter cutoff frequency, resistor value, and Q factor to get exact component values.
Standard Resistor Calculator
Match a target resistance to the nearest E-series preferred value (E6, E12, E24, E48, E96). Shows the closest standard resistor, percentage error and the part's color-code bands.
Subwoofer Box Calculator
Design sealed and ported subwoofer enclosures from Thiele-Small parameters. Get recommended internal volume, tuning frequency and port dimensions for your driver.
Voltage Drop Calculator
Calculate voltage drop across a wire or cable using current, length, cross-sectional area, and conductor material. Supports copper and aluminum in both metric and AWG sizes.
Wheatstone Bridge Calculator
Calculate the unknown resistance in a Wheatstone Bridge circuit. Enter three known resistor values and find the fourth when the bridge is balanced.
Whip Antenna Length Calculator
Calculate whip and vertical antenna element lengths for quarter-wave, half-wave and 5/8-wave designs. Includes velocity factor correction and length conversion to cm, inches and feet.
Zener Diode Calculator
Design Zener diode voltage regulator circuits. Calculate the series resistor value, Zener current, load current, and power dissipation from input voltage and load requirements.
Frequently asked questions
Which resistor color bands are supported?
Four and five band codes, both directions — color to value and value to colors, with tolerance included.
Do the filter tools give component values?
Yes — for standard topologies you choose the cutoff and order; the tools return component values within E-series preferences.
Are RF results valid for any distance?
Formulas assume far-field conditions; the pages state the limits so near-field or heavily obstructed setups are flagged.