Signal Integriry

Calculate the required trace width for a specified current
https://www.eeweb.com/tools/external-pcb-trace-width

Calculate the maximum current of an internal trace
https://www.eeweb.com/tools/internal-pcb-trace-max-current

Creepage
https://pcbdesign.smps.us/creepage.html

Characteristic Impedance of Traces
https://www.eeweb.com/tools/microstrip-impedance

Characteristic Impedance of Cable
https://www.eeweb.com/tools/coax

Crosstalk
https://www.eeweb.com/tools/microstrip-crosstalk

RLC Calculator

PCB Trace Resistance Calculator
https://www.eeweb.com/tools/trace-resistance

Inductance Calculator
https://www.eeweb.com/tools/wire-self-inductance-calculator

Capacitance Calculator
https://chemandy.com/calculators/rectangular-capacitor-calculator.htm

Losses

Microstrip Line Loss
https://www.microwaves101.com/calculators/1201-microstrip-calculator

Strip Line Loss
https://www.microwaves101.com/calculators/1202-stripline-calculator

Cable Loss
https://www.timesmicrowave.com/Calculator

Losses

Microstrip Line Loss
https://www.microwaves101.com/calculators/1201-microstrip-calculator

Strip Line Loss
https://www.microwaves101.com/calculators/1202-stripline-calculator

Cable Loss
https://www.timesmicrowave.com/Calculator