Tools
Free tools for makers
Everything here runs in your browser, needs no account, and is free. Most of it exists because we got tired of doing the same arithmetic on a bench notepad.
Code → BOM → Cart
Paste an Arduino or ESP32 sketch and get the parts it needs, matched against live stock and ready to add to the cart in one go.
Compatibility checker
Check logic levels, supply voltage and current draw between a board and a module before you wire 5 V into a 3.3 V pin.
Electronics calculators
Ten calculators covering resistors, LEDs, dividers, 555 timers, RC and LC networks, and battery runtime.
Build assistant
Describe what you're making and get a component list, wiring notes and the gotchas worth knowing before you start.
Calculators
Every calculator
Individually linkable, so you can bookmark the one you use every week.
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.