Free Tool
Trace width calculator.
Sanity-check your copper width vs. target current per IPC-2152. Same chart we use when quoting heavy-copper and power boards.
| I | Outer | Inner | ΔT |
|---|---|---|---|
| 1 A | 6 mil | 15 mil | +10 °C |
| 3 A | 20 mil | 50 mil | +10 °C |
| 5 A | 40 mil | 120 mil | +20 °C |
| 10 A | 120 mil | 300 mil | +30 °C |
Under the Hood
Five factors that drive trace width
Thermal headroom
Never size the trace alone — size the thermal path
IPC-2152 gives you a width, but a trace doesn’t sit in free air. Stack-up, copper pours, via density and ambient temperature all change the answer. When in doubt, widen the trace by 20% and sleep well.
- Plane copper next to the trace helps cool it
- Vias along the path double as heatsinks
- Derate 20% for high-density boards
- Outer layers run ~2.5× cooler than inner
- Above 10 A, split into parallel traces
- Above 30 A, use copper pours or bus bars
Frequently Asked Questions
Trace width calculator FAQ
01Outer layer vs inner layer — why is the difference so big?
Outer layers dissipate heat to ambient air and dominate cooling. Inner layers are sandwiched in dielectric (~0.3 W/m·K) — heat conduction out is much slower, so you need ~2.5× more copper width for the same current.
02What ΔT should I pick?
For safety-critical products: +10 °C. For standard industrial: +20 °C. Short-duration bursts: up to +30 °C. Never design for more than the laminate’s Tg minus ambient.
03Does the calculator account for vias?
No — trace width only. For vias, derate: a plated through-hole via (0.3 mm drill, 1 oz plating) carries ~1 A with +10 °C rise. Use multiple vias for high-current transitions.
04Do you offer other calculators?
Yes — see all tools: impedance, voltage drop, conduit fill, wire size.
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