Tools
Each one names the standard it implements and the assumptions it makes. An uncited calculator is just a number generator.
| Sym | Tool | Solves for | Basis |
|---|---|---|---|
| w | Trace width | mils / mm | IPC-2221 |
| R | Resistor decoder | ohms | IEC 60062 / 60063 |
| fc | RC filter | hertz | First-order passive |
| Z0 | Microstrip impedance | ohms | IPC-2141 |
| Vo | Voltage divider | volts | Ohm's law |
| e% | Baud rate error | per cent | Integer-divisor UART |
| Iv | Via | amps / ohms / K/W | IPC-2221 / IPC-6012 |
| Rp | I²C pull-up | ohms | NXP UM10204 |
| CL | Crystal load | picofarads | ST AN2867 |
| Rs | LED resistor | ohms | Ohm's law |
| C | Capacitor code | farads | IEC 60062 / EIA-198 |
| t | Battery runtime | hours / days | Time-weighted average |
| |Z| | Decoupling | ohms vs hertz | Series RLC / target impedance |
| RT | RS-485 bus | termination / bias | TIA-485 / TI SLLA272 |
| Q | Active filter | R and C values | TI SLOA049 |