Free online calculator
Example AWG 18 — Ø 1.024 mm — 0.823 mm² — 20.95 mΩ/m — nearest metric size 0.75 mm²
The gauge is geometric, not a lookup table: mm, and . Resistance assumes copper at 20 °C.
What you enter
Controlled impedanceA trace over a single reference plane, solved backwards from IPC-2141's own closed-form approximation: . Good to a few percent for 0.1 ≤ w/h ≤ 2 — the…
Heatsink / thermal— the heatsink only gets what is left of the budget after the package and the interface have taken theirs.
PCB trace ampacityEmpirical IPC-2221 formula — a design estimate, not a manufacturer guarantee.
Wire voltage drop, where for a round trip. The ohms per metre come from the AWG table.
Battery life— efficiency is entered as a percentage and applied as a fraction.
BJT base resistorA transistor used as a switch is not an amplifier — you deliberately throw its gain away. The mistake is dividing the load current by the datasheet hFE:…
Crystal load capacitorsA crystal's datasheet states its load capacitance Cₗ. The two caps sit in series as seen by the crystal, and the board adds stray capacitance Cₛ (~3–5 pF…