Electronics · Free Calculator
PCB Trace Width Calculator (IPC 2221)
Find the minimum PCB track width for a given current and allowed temperature rise, using the IPC 2221 formula.
IPC 2221External and internalmm and milCopper weight
A
°C
Minimum trace width0.781 mm
Width in mil30.8 mil
Cross section42.39 mil²
Copper thickness1.38 mil (35 µm)
How this result was calculated
- A = (I ÷ (k × ΔT0.44))1/0.725 with k = 0.048 → 42.39 mil²
- W = A ÷ thickness = 42.39 ÷ 1.38 = 30.8 mil (0.781 mm)
Advertisement
IPC 2221 Trace Width Formula
I = k × ΔT0.44 × A0.725
A (mil²) = (I ÷ (k × ΔT0.44))1/0.725
W = A ÷ (1.378 × copper oz)
A (mil²) = (I ÷ (k × ΔT0.44))1/0.725
W = A ÷ (1.378 × copper oz)
k = 0.048 for external layers and 0.024 for internal layers. 1 oz copper is 1.378 mil (35 µm) thick. IPC 2152 is the newer standard and is less conservative for internal layers.
Worked example
2 A on a 1 oz outer layer with 10 °C rise needs A = 42.4 mil², so W = 30.8 mil (0.78 mm). On an inner layer the same current needs about 2.6 times the width.
Key insight: inner layers run hotter because they cannot shed heat to air, which is why IPC 2221 uses half the k factor for them.
Advertisement
Frequently Asked Questions
How wide should a PCB trace be for 1 A?
About 0.3 mm (12 mil) on a 1 oz outer layer for a 10 °C rise.
Why are internal traces wider for the same current?
They are surrounded by FR4, which conducts heat poorly, so IPC 2221 halves the current capacity.
What is the difference between IPC 2221 and IPC 2152?
IPC 2152 is based on newer test data and accounts for board thickness and planes; IPC 2221 is simpler and more conservative.
You May Also Like
Learn more on the blog
PCB design fundamentals
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
Read Full ArticleMore Electronics Calculators
SMD Resistor Code Calculator3 digit (472), 4 digit (1002)Capacitor Code Calculator3 digit code, Tolerance letterStandard Resistor Values Calculator (E Series)E6 and E12, E24 (5 %)Inductors in Series and Parallel CalculatorSeries, ParallelAir Core Coil Inductance CalculatorWheeler formula, Single layer coilResistor Power Rating CalculatorP = V²/R, P = I²RCurrent Divider CalculatorTwo or three branches, Branch currentWheatstone Bridge CalculatorBalance condition, Output voltageRC and RL Filter Cutoff Frequency CalculatorLow pass, High passRLC Circuit Impedance CalculatorSeries RLC, Parallel RLCLED Series and Parallel Array CalculatorLEDs per string, String resistorTransistor Base Resistor CalculatorBJT switch, SaturationInverting Op Amp Amplifier CalculatorGain = −Rf/Rin, Output voltageNon Inverting Op Amp Amplifier CalculatorGain = 1 + Rf/Rg, Output voltageOp Amp Differential Amplifier CalculatorVout = (R2/R1)(V2 − V1), Four resistorsOp Amp Summing Amplifier CalculatorOp amp adder, Weighted sumInstrumentation Amplifier Gain Resistor CalculatorAD620, AD8221, INA128, INA333Op Amp Gain Bandwidth and Slew Rate CalculatorGBW ÷ gain, Slew rate555 Timer Astable CalculatorFrequency, Duty cycle555 Timer Monostable Calculatort = 1.1 RC, One shotCrystal Load Capacitor CalculatorC1 = C2, Load capacitanceFrequency to Period CalculatorHz to seconds, Period to HzPWM Duty Cycle CalculatorDuty cycle %, Average voltageLM317 Voltage Regulator CalculatorVout = 1.25(1 + R2/R1), R2 for targetZener Diode Series Resistor CalculatorSeries resistor, Zener powerLinear Regulator Power Dissipation CalculatorPower dissipation, Junction temperatureHeat Sink Thermal Resistance CalculatorθSA in °C/W, Junction temperatureBuck Converter CalculatorDuty cycle, Inductor valueBoost Converter CalculatorDuty cycle, Inductor valueRectifier Filter Capacitor CalculatorSmoothing capacitor, Ripple voltagePCB Trace Resistance CalculatorCopper resistance, Voltage dropBinary, Decimal, Hex and Octal ConverterBinary, HexadecimalBattery Life Calculator for Electronic DevicesmAh capacity, Sleep currentdBm to Watts CalculatordBm to mW, Watts to dBmResistor Color Code Calculator4 band, 5 bandLED Resistor CalculatorSingle LEDVoltage Divider CalculatorOutput and resistor valuesResistors in Series and ParallelTotal resistanceOhm's Law CalculatorV, I, R and PRC Time Constant CalculatorCharge and dischargeReactance CalculatorXL and XCLC Resonant Frequency CalculatorTank circuitsCapacitors in Series and ParallelTotal capacitanceCapacitor Energy CalculatorJoules and chargeDecibel CalculatorPower and voltage ratiosADC Resolution CalculatorBits and LSB size
More Calculator Categories
Temperature Measurement15 live toolsInstrumentation Signal4 live toolsPLC Digital Signal3 live toolsFlow Measurement19 live toolsLevel Measurement12 live toolsPressure Measurement13 live toolsControl Valve12 live toolsCalibration10 live toolsSafety and SIL7 live toolsAnalytical8 live toolsElectrical37 live toolsUnit Converters76 converters, 700+ units