For makers, hobbyists & hardware builders
The electronics calculators you reach for at the bench — fast, correct, no clutter.
Resistor codes, LED resistors, dividers, filters, 555 timers, battery runtime and IPC-2221 trace widths. Real E-series values, not just ideal numbers. Free, no sign-up.
Free calculators
Resistor Color Code
Read 4, 5 and 6-band resistors, or find the bands for a value.
💡LED Resistor
Pick the current-limiting resistor and its power rating.
➗Voltage Divider
Output voltage, loading effect and best E-series resistor pair.
〰️RC Filter
Cutoff frequency, time constant and attenuation at any frequency.
📻LC Resonance
Resonant frequency, characteristic impedance and Q.
⏱️555 Timer
Astable frequency/duty cycle and monostable pulse width.
🔋Battery Life
Runtime from capacity, active/sleep current and duty cycle.
🧵PCB Trace Width
IPC-2221 trace width for your current and temperature rise.
🔁Electronics Unit Converter
SI prefixes, AWG ↔ mm², mil ↔ mm, dBm ↔ mW, oz copper.
Real parts, not ideal ones
Every resistor result comes with the nearest E12/E24/E96 value, the error it introduces and the power rating to buy.
Type like an engineer
Enter 4k7, 100n or 2M2. Values parse the way they're printed on schematics.
Pro for real projects
Save results into projects, cost a whole BOM, estimate battery runtime from every part, and export PDF or CSV.
Simple pricing
The calculators stay free. Pro is for people building real boards.
Free
$0 forever
- ✓All 9 core calculators
- ✓Reverse lookups & E-series rounding
- ✓Works on phone at the bench
- ✓No sign-up
Pro Monthly
$4 per month, cancel anytime
- ✓Everything in Free
- ✓Saved projects (in your browser)
- ✓Batch BOM cost & battery-runtime calculator
- ✓PDF & CSV export of any result
- ✓Ad-free
- ✓Support an independent tool
Pro Lifetime
$29 one-time payment
- ✓Everything in Free
- ✓Saved projects (in your browser)
- ✓Batch BOM cost & battery-runtime calculator
- ✓PDF & CSV export of any result
- ✓Ad-free
- ✓Support an independent tool
- ✓All future calculators included
Prices in USD. Taxes may apply and are calculated at checkout by Creem, our Merchant of Record. 14-day refund on first purchase — see refund policy. Already paid? Restore purchase.