Microstrip Impedance Calculator
PCB Trace Width, Current and Impedance Calculator works out Minimum trace width (IPC-2221) and Minimum trace width from What to solve for, Trace current and Allowed temperature rise. The default figures on this page give minimum trace width (IPC-2221) of 11.895 mil; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
10 steps
- Copper thickness = 1.37 mil (34.8 um)
- IPC-2221 area: A = (I / (k * dT^0.44))^(1/0.725) = (1 / (0.048 * 2.754229))^1.37931 = 16.296 mil^2
- Minimum width = A / thickness = 16.296 / 1.37 = 11.8949 mil (0.3021 mm)
- Capacity of a 10 mil trace: I = 0.048 * 10^0.44 * 13.7^0.725 = 0.8818 A
- R(20 C) = rho * L / A = 1.724e-8 * 0.1 / 1.051353e-8 = 0.1639792 ohm
- R(35 C) = R20 * (1 + 0.00393 * (35 - 20)) = 0.17364578 ohm; drop = 0.17365 V, dissipation = 0.17365 W
- Microstrip Z0 = (87/sqrt(4.3+1.41)) * ln(5.98*10 / (0.8*10 + 1.37)) = 67.483 ohm
- Differential Z = 2*Z0*(1 - 0.48*exp(-0.96*s/h)) with s = 8 mil gives 104.91 ohm
- Propagation delay = 139.992 ps/in (5.5115 ps/mm); Z0 = tpd/C gives 2.0745 pF/in and 9.447 nH/in
- Width solved for 50 ohm: 17.219 mil (0.4374 mm)
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
5 sources
What the PCB Trace Width, Current and Impedance Calculator calculates
Sizes a printed-circuit conductor from current and temperature rise using IPC-2221, reports its current capacity, DC resistance and voltage drop, and computes microstrip / stripline single-ended and differential impedance and propagation delay per IPC-2141A.
How to use this PCB Trace Width, Current and Impedance Calculator
Enter What to solve for, Trace current, Allowed temperature rise and Conductor location. Minimum trace width (IPC-2221) updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Minimum trace width (IPC-2221), Minimum trace width and Required cross-section.
The method follows IPC-2221B/C, Generic Standard on Printed Board Design, conductor current-carrying capacity (I = k dT^0.44 A^0.725), IPC-2141A, Design Guide for High-Speed Controlled Impedance Circuit Boards (microstrip, stripline, differential and propagation delay equations), Polar Instruments, "Calculation of PCB Track Impedance" (IPC equation forms and their validity ranges), NIST / IACS: annealed copper resistivity 1.724e-8 ohm*m at 20 C, temperature coefficient 0.00393 per degree C and IPC-4562A / IPC-6012: nominal 1 oz/ft^2 copper foil = 1.37 mil = 34.8 um.
1 A, 10 C rise, 1 oz external copper example
With What to solve for: width-from-current, Trace current: 1, Allowed temperature rise: 10, Conductor location: external, the calculator returns Required cross-section: 16.2965, Minimum trace width (IPC-2221): 11.8953, Copper thickness: 1.37. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Minimum trace width (IPC-2221), Minimum trace width and Required cross-section. The inputs you can vary are What to solve for, Trace current, Allowed temperature rise, Conductor location, Copper weight and Copper thickness override.
Understanding Minimum trace width (IPC-2221), Minimum trace width and Required cross-section
IPC-2221 conductor sizing is a conservative chart fit and IPC-2152 supersedes it for production current-capacity work. Have conductor sizing for safety-critical, high-current or high-voltage designs reviewed by a qualified PCB engineer against the applicable IPC standard and any product safety standard (e.g. IEC 62368-1) before release.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
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Frequently asked questions
What information do I need for the PCB Trace Width, Current and Impedance Calculator?
You need What to solve for, Trace current, Allowed temperature rise, Conductor location, Copper weight, Copper thickness override, Thickness per ounce of copper and Trace width. The page opens with default figures that give minimum trace width (IPC-2221) of 11.895 mil, so you can see the scale before entering your own.
What does this PCB Trace Width, Current and Impedance Calculator show?
It shows Minimum trace width (IPC-2221), Minimum trace width, Required cross-section, Current capacity of the entered width, Copper thickness, Width used for resistance, DC resistance at temperature and Resistance per inch, with the working and any warnings for your entries.
Can I check how the PCB Trace Width, Current and Impedance Calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.