Laptop Charger Connector Sizes Explained: 4.5mm, 5.5mm, 7.4mm and USB-C
XiongYing Zeng
Here's a frustrating way to waste money: order a charger with the perfect voltage and wattage, wait for it to arrive, and discover the plug won't go into your laptop. Connector mismatch is the single biggest cause of charger returns, and it's entirely avoidable once you understand how barrel tips are measured and which sizes the major brands use.
This is the practical, no-jargon guide to identifying your connector — the numbers that describe it, how to measure it if you're not sure, and the trap of barrel tips that look identical but aren't.
How barrel connectors are measured
A traditional round "barrel" plug is described by two measurements, always written outer × inner:
- Outer diameter (OD) — the width of the metal barrel itself, e.g. 5.5mm.
- Inner diameter (ID) — the hole down the middle, which slides over a pin inside the laptop's port, e.g. 2.5mm.
So a tip written 5.5 × 2.5mm has a 5.5mm outer barrel and a 2.5mm inner hole. Many higher-wattage gaming plugs also have a small center pin inside the hole, which carries an identification or sense signal. Both numbers — and the presence of a center pin — have to match your laptop's port. A 5.5 × 2.5mm tip will not seat properly in a port built for 5.5 × 1.7mm, even though the outer size is the same.
The common sizes, by brand
Barrel sizes aren't standardized across the industry, but each brand tends to stick to a couple. This is a starting point, not a guarantee — always confirm against your own adapter:
| Connector | Often seen on |
|---|---|
| 4.5 × 3.0mm (blue tip, center pin) | HP (OMEN, Victus, Pavilion, ZBook), Dell ultrabooks |
| 5.5 × 1.7mm | Acer (Predator, Nitro, Aspire) |
| 5.5 × 2.5mm | Older ASUS, Toshiba, many generic laptops |
| 6.0 × 3.7mm (center pin) | ASUS ROG / TUF / Zephyrus (pre-2024) |
| 7.4 × 5.0mm (center pin) | Dell (Alienware, G-series, Precision), older HP |
| Rectangular "slim tip" | Lenovo (Legion, ThinkPad, IdeaPad) |
| USB-C | Modern ultrabooks and many 2023+ machines |
Same number, different brand ≠ compatible. A Dell 7.4mm plug and an HP 7.4mm plug can look identical but carry different voltages or pin layouts. Matching the millimetre size is necessary but not sufficient — the voltage and the laptop's expectations have to line up too. Never assume cross-brand compatibility from the barrel size alone.
How to identify yours
You have three easy options, in order of reliability:
- Read it off the listing or label. Many original adapters and replacement listings print the tip size directly. Your laptop's spec sheet or manual may state it too.
- Match by laptop model. Search your exact model number plus "charger connector size" — for a known model, the tip is documented.
- Measure it. With calipers (or a ruler in a pinch), measure the outer diameter of the metal barrel. The inner diameter is harder to eyeball, so this is a last resort — but the OD alone often narrows it down a lot.
USB-C: the connector that ended the guessing
Modern laptops increasingly charge over USB-C Power Delivery, which sidesteps the whole barrel-size problem — the connector is universal and reversible. The catch moves from shape to power: a USB-C charger has to supply enough wattage for your laptop and support the right PD profile. So with USB-C you stop worrying about millimetres and start checking that the wattage is high enough. For higher-power gaming laptops, USB-C is often only a partial-speed backup, with the barrel adapter still needed for full performance.
👉 Know your connector? Match it along with your voltage and wattage. Browse compatible laptop chargers → — listings state the exact tip size so the plug fits the first time.
FAQ
What do the two numbers in a connector size mean?
They're the outer diameter and inner diameter of the barrel, written outer × inner — for example 5.5 × 2.5mm means a 5.5mm outer barrel with a 2.5mm inner hole. Both must match your laptop's port, along with any center pin.
Are laptop charger tips universal?
No. Sizes vary by brand and even by model. A tip that fits one laptop may be the wrong outer or inner diameter for another, and matching the size doesn't guarantee the voltage is right. Always confirm both the connector and the electrical specs.
Can I use an adapter or converter tip?
Sometimes. Some chargers ship with interchangeable tips, and HP historically offered a 4.5-to-7.4mm dongle. A quality converter that delivers the correct voltage and wattage can work, but a loose or mismatched tip is a common point of failure, so confirm the fit is snug and the specs are right.
How do I measure my charger's connector?
Measure the outer diameter of the metal barrel with calipers; that's the easiest number to get. The inner diameter is trickier, so if you can identify the tip from your laptop model or the adapter label instead, that's more reliable.
Is USB-C charging the same on every laptop?
The connector is universal, but the power isn't. A USB-C charger must meet your laptop's required wattage and support the correct Power Delivery profile. Lower-wattage USB-C chargers may only trickle-charge a power-hungry laptop.
A barrel connector is two numbers — outer × inner — plus maybe a center pin, and all of them have to match your port. Sizes differ by brand, and the same millimetres on a different brand can still be the wrong charger. Identify yours from the label, your model, or a quick measurement, and for USB-C, match the wattage instead of the shape.
Find a charger with the right connector →
The full spec-matching process is in our complete laptop charger buying guide. Shopping for a specific brand? See the guides for Acer, Dell & Alienware, and HP OMEN.
Brand names are used solely to describe compatibility and do not indicate any affiliation. Always verify the connector size and electrical specs against your laptop's original adapter before purchasing.
