Tools
Electronics Calculators
All the calculators a maker needs — free, instant, no account required.
Resistor Color Code
Decode 4- or 5-band resistor color codes to values, or find bands for a known resistance.
LED Series Resistor
Calculate the correct current-limiting resistor for any LED — shows power dissipation and nearest E12 value.
Voltage Divider
Find Vout for any R1/R2 pair, or solve backwards for a target output voltage.
555 Timer
Astable and monostable modes — frequency, period, duty cycle, and pulse width from R and C values.
Ohm's Law & Power
Enter any two of V, I, R, P and solve for the other two instantly.
Series / Parallel Resistors
Add up to 8 resistors in any series/parallel combination and find the equivalent resistance.
RC Time Constant
R and C to τ, charge/discharge times, and -3 dB cutoff frequency.
LED Array
Design series-parallel LED arrays: resistor per branch, total current and power.
Battery Life
Estimate runtime from battery capacity, load current and efficiency factor.
LC Resonance
Find the resonant frequency of an LC circuit, or solve for the missing component value.