50 Ohm Trace Width Calculator Formula
50 Ohm Trace Width Calculator Feet

ANSI PCB Trace Width Calculator

Trace Width Calculator FAQs Q: Is there a limit to the amount of current this tool can calculate a width for? The IPC-2221 data from which these formulas are derived only covers up to 35 Amps, trace width up to 400 mils, allowable temperature rise from 10 to 100 degrees Celsius, and copper of 0.5 to 3 ounces per square foot. Another idea (but its going to be more expensive) is making a PCB of more than 2 layers. With 3 layers and a trace width of 0.7mm, the characteristic impedance should be around 75ohm. With 4 layers and a trace width of 0.7mm, the characteristic impedance should be around 60ohm, but with 1mm of width, should be around 49ohm.

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New features in this version include:

use of metric or imperial units for all major fields
the ability to change units for any applicable field on the fly
minor enhancements to some of the calculations - IPC-2221(A) changes the curve fit
saving of all parameters in a cookie to keep your preferences between visits

ANSI PCB Trace Width Calculator
Input Data			Results Data
Internal Traces		External Traces
Field	Value	Units	Trace Data	Value	Units	Value	Units
Current (max. 35A)	Required Trace Width
Temperature Rise (max. 100°C)	Cross-section Area
Cu thickness	Resistance	Ω Ohms	Ω Ohms
Ambient Temperature	Voltage Drop	Volts	Volts
Conductor Length	Loss	Watts	Watts
Peak Voltage	Volts	Required Track Clearance

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 Trace Currents and Temperatures Revisited by Douglas Brooks, UltraCAD Design, Inc.

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 dT^0.44 x A^0.725
External traces: I = 0.048 x dT^0.44 x A^0.725

where:

50 Ohm Trace Width Calculator Formula

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:

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.
Ideally, keep 'hot' and 'cold' areas of your board well apart.

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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ANSI PCB Trace Width Calculator

50 Ohm Trace Width Calculator Formula

50 Ohm Trace Width Calculator Feet