Electronics calculators that just work
Fast, accurate engineering tools — built by an electronics engineer, free to use, no sign-up.
All calculators
Basics
Resistor Code Decoder (THT & SMD)
Decode through-hole color bands or SMD codes.
Ohm's Law Calculator
V, I, R and P from any two known values.
Resistor Combination & Standard Values
Series/parallel totals plus nearest E-series value.
Op-Amp Gain Calculator (Inverting & Non-Inverting)
Gain and output voltage for both op-amp configurations.
Capacitor Code Decoder (Ceramic EIA & Film Markings)
Decode 3-digit ceramic codes and film cap letter markings.
BJT Bias Resistor Calculator (Voltage Divider)
R1/R2/Rc/Re for a common-emitter NPN stage.
Passive
LED Series Resistor Calculator
Pick the right resistor for any LED and supply voltage.
Voltage Divider Calculator
Compute output voltage, current and resistor ratios.
LC Filter Cutoff Frequency Calculator
Compute resonance / cutoff for LC, RC and RL filters.
RC Time Constant Calculator
Time constant and cutoff frequency from R and C.
555 Timer Calculator
Astable frequency, duty cycle and monostable pulse width.
Rectifier Smoothing Capacitor Calculator
Capacitor value from load current and ripple.
Sealed Speaker Box Volume Calculator
Sealed enclosure volume from driver Vas, Qts and Fs.
MCU / Embedded
Crystal Load Capacitance Calculator
Pick C1/C2 for a target crystal load capacitance.
ADC Calculator (bits, LSB, voltage)
Convert ADC code to voltage and LSB size.
UART Baud Rate Error Calculator
Best BRR/divisor and error from clock and baud.
PCB
PCB Trace Width Calculator (IPC-2221)
Required trace width for a given current and copper weight.
Microstrip Impedance Calculator
Estimate characteristic impedance from your PCB stackup.
RF
Smith Chart Impedance Matching Calculator
Plot impedance, read Γ, VSWR, and matching values.
dB ↔ Power / Voltage Converter
Convert between dB, power and voltage ratios.
Antenna Length Calculator (Dipole & Monopole)
Half-wave dipole and quarter-wave monopole length from frequency.
Power
Battery Life Calculator
Runtime from capacity, current draw and efficiency.
Voltage Drop & Wire Gauge Calculator
Required cross-section for length, current and drop.
Wire Ampacity Calculator (AWG / mm²)
Safe continuous current for a wire gauge and insulation rating.
Zener Diode Shunt Regulator Calculator
Series resistor value from Vin, Vz and Iz.
Buck/Boost Converter Duty Cycle Calculator
Ideal CCM duty cycle from Vin and Vout, both topologies.
Heatsink Thermal Resistance Calculator
Required Rth(s-a) from power, junction temp and Rth(jc/cs).
Current Sense (Shunt) Resistor Calculator
Shunt resistor value and power dissipation for current sensing.
RC Snubber Calculator (Switching Node)
Snubber R and C from parasitic L/C or ring frequency.