Specifications
| Outside diameter | 4.0 mm |
|---|---|
| Hole diameter | 1.35 mm |
| Centre pin in the hole | no |
| Standard | de facto size |
| Rating (catalogue part) | no published rating |
| Polarity | not set by the size: read the symbol |
Lookalikes and how to tell them apart
Same 4.0 mm outside as EIAJ class 2 (4.0 × 1.7), which is meant for 3.15–6.3 V, but a smaller hole: a 1.7 plug wobbles on its pin. The 3.8 × 1.35 is a little thinner.
| Size | Centre pin | Standard |
|---|---|---|
| 4.0 × 1.35 mm | no | de facto size |
| 4.0 × 1.7 mm | no | EIAJ class 2, 3.15–6.3 V |
| 3.8 × 1.35 mm | no | de facto size |
| 3.5 × 1.35 mm | no | de facto size |
Before you plug it in
Measure with a caliper: the metal sleeve gives the outside diameter. For the hole, use drill bits as gauges: the largest one that slides in gives the size. If there is a pin in the middle, a bit won’t go in: use the caliper’s inside jaws.
The size says nothing about polarity: look for the symbol (a dot inside a C, with + and −) on the device and on the adapter. Centre positive is the most common.
Open the connector identifier →Not sure it is this size? Enter the outside and hole diameters: the identifier compares 22 DC plug sizes.
Other DC plug sizes
2.0 × 0.6 mm 2.35 × 0.7 mm 2.5 × 0.7 mm 3.0 × 1.1 mm 3.5 × 1.1 mm 3.5 × 1.35 mm 4.0 × 1.7 mm 4.5 × 3.0 mm 4.75 × 1.7 mm 4.8 × 1.7 mm 5.5 × 1.7 mm 5.5 × 2.1 mm 5.5 × 2.5 mm 5.5 × 3.0 mm 5.5 × 3.3 mm 6.3 × 3.0 mm 6.5 × 4.4 mm 7.4 × 5.0 mm 7.9 × 5.5 mm
All DC plug sizes, with a chart →
Frequently asked questions
Does a 4.0 × 1.35 mm plug fit a 4.0 × 1.7 mm jack?
No: its 1.35 mm hole doesn’t go over the thicker pin of a 4.0 × 1.7 mm jack.
Is 4.0 × 1.35 mm a standard size?
No: it is a de facto size, common but not set by IEC or EIAJ. Check the voltage and polarity on the label.
Sizes and ratings from the makers’ catalogues (Same Sky, Lumberg, Switchcraft) and the EIAJ and IEC summaries. A plug’s rating is a maximum: the adapter’s label says what it actually supplies.