How to use the PCB trace width calculator
- Choose width from current, or current from width.
- Enter the current (or width), temperature rise, copper weight and layer.
- Add the trace length to see voltage drop and power loss.
PCB trace width vs current chart (IPC-2221, 10 °C rise)
IPC-2221 gives I = k × ΔT^0.44 × A^0.725 (A in mil², k = 0.048 outer, 0.024 inner). Inner layers shed heat poorly and need about 2.6 times the width for the same current. The fit covers up to 35 A, 400 mil and a 10–100 °C rise; check high currents and dense boards against IPC-2152 or a thermal simulation.
| Current | Outer 1 oz | Outer 2 oz | Inner 1 oz | Inner 0.5 oz |
|---|---|---|---|---|
| 0.25 A | 0.04 mm (1.8 mil) | 0.02 mm (0.9 mil) | 0.12 mm (4.6 mil) | 0.23 mm (9.1 mil) |
| 0.5 A | 0.12 mm (4.6 mil) | 0.06 mm (2.3 mil) | 0.3 mm (11.9 mil) | 0.6 mm (23.8 mil) |
| 1 A | 0.3 mm (11.9 mil) | 0.15 mm (5.9 mil) | 0.79 mm (31 mil) | 1.57 mm (61.9 mil) |
| 1.5 A | 0.53 mm (20.8 mil) | 0.26 mm (10.4 mil) | 1.38 mm (54.1 mil) | 2.75 mm (108.3 mil) |
| 2 A | 0.79 mm (31 mil) | 0.39 mm (15.5 mil) | 2.05 mm (80.5 mil) | 4.09 mm (161 mil) |
| 3 A | 1.38 mm (54.1 mil) | 0.69 mm (27.1 mil) | 3.58 mm (140.9 mil) | 7.16 mm (281.7 mil) |
| 4 A | 2.05 mm (80.5 mil) | 1.02 mm (40.3 mil) | 5.32 mm (209.5 mil) | 10.64 mm (418.9 mil) |
| 5 A | 2.78 mm (109.5 mil) | 1.39 mm (54.8 mil) | 7.24 mm (285 mil) | 14.48 mm (569.9 mil) |
| 7.5 A | 4.87 mm (191.6 mil) | 2.43 mm (95.8 mil) | 12.66 mm (498.5 mil) | 25.32 mm (997 mil) |
| 10 A | 7.24 mm (285 mil) | 3.62 mm (142.5 mil) | 18.83 mm (741.3 mil) | 37.66 mm (1,482.6 mil) |
| 15 A | 12.66 mm (498.5 mil) | 6.33 mm (249.2 mil) | 32.94 mm (1,296.8 mil) | 65.88 mm (2,593.6 mil) |
| 20 A | 18.83 mm (741.3 mil) | 9.41 mm (370.6 mil) | 48.98 mm (1,928.4 mil) | 97.96 mm (3,856.8 mil) |
1 oz copper is about 35 µm. Values are minimums; also allow for voltage drop, impedance and fabrication margins.
Frequently asked questions
How wide should a trace be for 1 A?
Per IPC-2221 with 1 oz outer copper and a 10 °C rise, about 0.30 mm (12 mil); on an inner layer about 0.79 mm (31 mil). Designs usually add margin.
IPC-2221 or IPC-2152?
IPC-2221 is a fit to older test curves and is conservative for inner layers. IPC-2152 accounts for board thickness, copper planes and dielectric conduction and is closer to reality but needs more inputs. IPC-2221 is fine for most designs; check high-current boards with IPC-2152 or a thermal simulation.
What temperature rise should I use?
A 10 °C rise is common; 20–30 °C may be acceptable when space is tight, as long as ambient plus rise stays within the board and component ratings.
Are my inputs uploaded?
No. Everything is calculated locally in your browser and nothing is stored; a share link only carries the values you entered.
Results are for design estimates and part selection; for production and safety-related circuits follow component datasheets, applicable standards and measurements.