PCB Copper Trace Width, Resistance & Voltage Drop Calculator (IPC-2221)

Size external PCB copper traces per IPC-2221 for current and temperature rise.

Minimum External PCB Trace Width
2.39 mm
Trace Width in Mils (thousandths in) 94.15 mils
Trace DC Resistance 12.43 mΩ
Voltage Drop Along Trace 55.94 mV
Inputs
A
Continuous trace current in Amperes (A).
oz
Copper cladding thickness in oz/ft² (1 oz = 1.378 mils / 35 μm).
°C
Allowable trace temperature rise above ambient (°C).
mm
Total trace length in millimeters.
Results & Graph
Minimum External PCB Trace Width
2.39 mm
Trace Width in Mils (thousandths in)
94.15 mils
Trace DC Resistance
12.43 mΩ
Voltage Drop Along Trace
55.94 mV

Minimum External PCB Trace Width

Graph 1 • Current Amps Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 mm 2.3 mm 4.5 mm 50%: 0.92 mm 0.9 50% 75%: 1.61 mm 1.6 75% 100%: 2.39 mm 2.4 100% 125%: 3.25 mm 3.3 125% 150%: 4.18 mm 4.2 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Minimum External PCB Trace Width 2.39 mm Trace Width in Mils (thousandths in) 94.15 mils Trace DC Resistance 12.43 mΩ Voltage Drop Along Trace 55.94 mV
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Minimum External PCB Trace Width2.39 mmTrace Width in Mils (thousandths in)94.15 milsTrace DC Resistance12.43 mΩVoltage Drop Along Trace55.94 mV
Summary: Carrying 4.5 A on 1 oz copper with a 10°C rise requires a 2.39 mm (94.1 mil) external trace.
Summary: Carrying 4.5 A on 1 oz copper with a 10°C rise requires a 2.39 mm (94.1 mil) external trace.
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Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: PCB Trace Width Physics & Engineering Equation

Areamils² = [ I / (0.048 × ΔT0.44) ]1 / 0.725
Widthmils = Areamils² / (CopperOz × 1.378)
Area_mils² = [ I / (0.048 × ΔT^0.44) ]^(1 / 0.725); Width_mils = Area_mils² / (CopperOz × 1.378)
  • currentAmps: Current Amps (A)
  • copperWeightOz: Copper Weight Oz (oz)
  • tempRiseCelsius: Temp Rise Celsius (°C)
  • traceLengthMm: Trace Length Mm (mm)

Rounding: Physical constants follow CODATA/NIST values; output quantities display to 2 decimal places.

Worked Example: Physics & Engineering Benchmark: PCB Trace Width

Size external PCB copper traces per IPC-2221 for current and temperature rise.

  1. Enter the physical dimensions, electrical parameters, or thermodynamic state variables.
  2. Apply the governing equation: Area_mils² = [ I / (0.048 × ΔT^0.44) ]^(1 / 0.725); Width_mils = Area_mils² / (CopperOz × 1.378).
  3. Inspect the primary SI output, derived quantities, and 3 visual SVG graphs.
Result: Computes PCB Trace Width via Area_mils² = [ I / (0.048 × ΔT^0.44) ]^(1 / 0.725); Width_mils = Area_mils² / (CopperOz × 1.378).

Frequently Asked Questions

What equation powers the PCB Copper Trace Width, Resistance & Voltage Drop Calculator (IPC-2221)?

It evaluates Area_mils² = [ I / (0.048 × ΔT^0.44) ]^(1 / 0.725); Width_mils = Area_mils² / (CopperOz × 1.378) using IEEE-754 double precision and renders three synchronized SVG plots.

Can I test parameter sensitivity across multiple values?

Yes. Graph 1 automatically plots a 50%–150% parameter response curve, and you can pin up to 3 custom scenarios.

Are all units consistent with SI standards?

Yes. Each input field specifies its exact SI or engineering unit and converts internally where needed.

Science & Engineering · Electrical & RF Engineering

PCB Copper Trace Width, Resistance & Voltage Drop Calculator (IPC-2221): inputs, method, and how to read the result

Size external PCB copper traces per IPC-2221 for current and temperature rise.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Current Amps: Continuous trace current in Amperes (A).
  • Copper Weight Oz: Copper cladding thickness in oz/ft² (1 oz = 1.378 mils / 35 μm).
  • Temp Rise Celsius: Allowable trace temperature rise above ambient (°C).
  • Trace Length Mm: Total trace length in millimeters.

What the calculation includes

With the default values shown, Minimum External PCB Trace Width is 2.39 mm. The calculation follows PCB Trace Width Physics & Engineering Equation; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Current Amps from 4.5 A to 4.95 A changes Minimum External PCB Trace Width from 2.39 mm to 2.73 mm. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard SI physical constants (g = 9.80665 m/s², c = 299,792,458 m/s, σ = 5.670374×10⁻⁸ W·m⁻²·K⁻⁴).
  • Engineering reference model; apply appropriate safety factors and empirical calibration for critical hardware designs.

Scope: SI / NIST Physics & Engineering Standard Check the assumptions and limitations against your situation before relying on the estimate.

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