ANSI IPC-2221A PCB Trace Width Calculator
ANSI PCB Trace Width Calculator
New features in this version include:
This page calculates approximations to the ANSI / IPC-2221/IPC-2221A design standards for PCB trace width - this is the replacement for IPC-D-275.
The approximations and rationale are described in Temperature Rise in PCB Traces, equations 13 & 15. by Douglas Brooks, UltraCAD Design, Inc. The original idea for this approach was from Brad Suppanz.
The figures returned by this calculator are to be taken as a guide only. I will not be held responsible for any mishap or loss, either direct or consequential, that may occur as a result of relying on the figures herein.
The trace width formulas are:
Internal traces : I = 0.024 x dT0.44 x A0.725
External traces: I = 0.048 x dT0.44 x A0.725
I = maximum current in Amps
dT = temperature rise above ambient in °C
A = cross-sectional area in mils²
Please note that IPC-2221(A) equations are subtly different from those in IPC-D-275 in that they are typically slightly more conservative and are impicitly derated to compensate for manufacturing effects, i.e. they should be more reliable in practice.
The values calculated here compare very closely with those derived by the UltraCAD PCBTEMP utility, and like the diagrams in the standards documents, are valid up to 35A for external traces and 17.5A for internal, 400mil widths and a maximum temperature rise of 100°C.
I've added a recommended track clearance value based on the UL rule:
clearance in inches = 0.023" + (0.0002" x V)
The formulae as it stands is simplistic, but is reasonable for V >
50. Note that there are many international standard for this sort of
thing, e.g. EN60065:1994, which for European mains of 230V, allows for
about 120mil for Class I (protected by earthing) and 240mil for Class II
(double isolated). Note that if there is no conformal coating and the
environment is dirty/humid/condensing then all bets are off. Please read
the standards documents yourself.
Change a value in an input field, then press TAB to move to the next field. The results tables will be updated automatically.
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