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PCB Trace Width Calculator January 31, 2006

This Javascript web calculator calculates the trace width for printed circuit boards based on a curve fit to IPC-2221 (formerly IPC-D-275). Also see the via calculator.

New features:


Current Amps

Optional Inputs:

Temperature Rise Deg
Ambient Temperature Deg
Trace Length

Results for Internal Layers:

Required Trace Width
Resistance Ohms
Voltage Drop Volts
Power Loss Watts

Results for External Layers in Air:

Required Trace Width
Resistance Ohms
Voltage Drop Volts
Power Loss Watts


The trace width is calculated as follows:

First, the Area is calculated:

Area[mils^2] = (Current[Amps]/(k*(Temp_Rise[deg. C])^b))^(1/c)

Then, the Width is calculated:

Width[mils] = Area[mils^2]/(Thickness[oz]*1.378[mils/oz])

For IPC-2221 internal layers: k = 0.024, b = 0.44, c = 0.725

For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725

where k, b, and c are constants resulting from curve fitting to the IPC-2221 curves

For geometry diagrams, click on the pictures below.

pcb-trace-geometry-2.png     pcb-trace-geometry-1.png

For frequently asked questions, see the comments.

PCB Trace Resistance Calculator January 24, 2006

This online web calculator finds the resistance of copper PCB traces (a.k.a. tracks) of given width, thickness, length, and temperature. It can also be used for copper bars (e.g. bus bars). Several choices of common units are available. Enter the Width and Thickness below. Optionally, enter the Temperature and Length, or just leave the default values. (To find the needed trace width based on current, see the PCB Trace Width Calculator.)

May 17, 2006 - Added (lateral) thermal resistance calculations.
January 18, 2007 - Clarified equations.

The Calculator

Best Free Circuit Simulator January 21, 2006

I have been using LTspice (a.k.a. SwitcherCAD III) for about 3 years as my main circuit simulation tool and have been very happy with it. Linear Technology has generously made it available free on their web site, and it is full-featured, fast, and seems to converge very well. I’ll be posting some of my simulation tips and tricks, so I highly recommend that you download it and get familiar with it. They also have a great user’s group to help get you going.

Find Standard Resistor and Capacitor Values

This javascript calculator finds the closest standard resistor (or capacitor) value in each of the IEA series. Use this, and get rid of that tattered old standard decade resistance table taped to your cubicle and put a nice photo there instead!

Desired Value:

IEA Series Closest Value Error

Which IEA series applies to the various component types?

Health Calculator

This post includes an online calculator that calculates how many calories you burn per day and your Body Mass Index (BMI).

Your Basal Metabolic Rate (BMR) is the calories needed for basic body function without any activity. Total Daily Energy Expenditure (TDEE) your BMR plus calories burned from activities. These can be helpful in planning food intake, diet, etc.

Body Mass Index (BMI)
The National Heart, Lung, and Blood Institute suggests the following:

The Calculator

Dynamic Excel Chart Colors January 17, 2006

Did you ever want to have the colors of an Excel bar chart change dynamically with the values of the chart? The code below gives results like those shown below.


Just place this code (more…)