Hard Drive Voltage – What they use, and why it matters.

Have you ever wondered what voltage a hard drive uses? We have and although the initial answer is simple some information might surprise you.

A hard drive’s voltage is determined by the standardized requirements of the SATA interface. SATA uses three voltages 3.3v, 5v, and 12v. Depending on the type of hard drive, it will use one of these or more commonly a combination. 

Different drives use different voltages for a number of different reasons, mainly this comes down to form factor and the size of the respective components.


Why 3.3v, 5v and 12v?

With the rise of personal computers, certain parts became standardized. This was done to create a marketplace of peripheral components that could be made by any manufacturer but plugged into any computer. These standardizations typically apply to specific interfaces like SATA or USB for example, manufacturers don’t have to use them but it is beneficial because doing so means they can reach the largest market because most consumers use them. A company like Apple which often designs their own interfaces do this to create a dependency on their own peripherals to compatible components. But even Apple still uses a majority of widely available interfaces and ports.

These standardizations become input parameters for designers and engineers creating products. The first hard drives were developed by IBM in the 50s and would not meet the requirements of most users today, initially, there were options like IDE connections or PATA, but the advent of SATA as a faster and more secure option came along and almost all hard drives began using it. What makes SATA so popular for manufacturers is not only the speed and security but also the fact it offers options. These options are 3.3v, 5v, and 12v. with various connections for each meaning that different components of a hard drive can have different voltages and the stepping down of the voltages doesn’t have to be done on the device itself.

The standardization not only sets parameters but also inherited them, so these seemingly arbitrary voltage numbers came from necessity. 5v was required to run the initial microchips in the first PCs and the 12v supply was required to run parts with motors like fans and hard drives. These voltages had already been standardized so it made sense to use them. Additionally, 3.3v was introduced as newer components that were more sensitive could make use of the smaller voltage.

Early drives used 5v for their logic boards and 12v for the motors. Newer drives take advantage of the different options while some only draw power from the 12v rail (supply) as the input and regulate the voltage themselves where needed. typically this is true of external drives.

Essentially what this means is that you could make a drive that used any voltage it required but unless you can regulate it from a 12v input there wouldn’t be any device you could use it with.

How can a hard drive use more than one voltage?

Hard drives consist of several components but can be narrowed down into motors and circuit boards. A motor is a mechanical part and in a hard drive is typically spun up to 7,500 rpm or 10,000 rpm in faster drives and even as fast as 15000 rpm in some disks like those designed for NAS storage. At 10,000 rpm the disk can reach speeds of up to 150 mph! Drives that reach this speed are usually bigger and are designed in the 3.5″ form factor. This in turn requires a higher voltage to reach peak RPM and so the 12v supply is needed.

The logic board inside a hard drive requires significantly less power to operate so typically uses the 5v or 3.3v supply. This can either come directly from the PSU rails or can be regulated by itself from a 12v input.

What voltage do External hard drives use?

This depends on the size of the hard drive itself. There are two form factors for HDDs 2.5″ and 3.5″.

Portable external hard drives are typically 2.5″ drives and use 5v. In theory, they can use up to 20v depending on the interface, for example, USB 2 can only provide 5v but USB – C can provide up to 20v. But this isn’t useful as the increased power wouldn’t result in faster read-write times in this form factor and it would mean that the HDD itself wasn’t recoverable from another enclosure.

Desktop external hard drives are typically 3.5″ form factor and need a 12v power supply. Depending on the interface, the drive may require a power brick to convert AC to DC so that when they are plugged into the mains the drive can be provided with the required 12v. For example, this wouldn’t be necessary with a USB – C drive plugged into a USB – C port, but if you used an adapter to plug it into a USB 2.0 port it wouldn’t work as it wouldn’t be able to draw enough power.

Why does my external hard drive not work with certain cables?

You may have noticed that when you try to plug in certain drives they work without power while others need a plug to the mains. Some work with certain cables and when you try other cables that have the same connectors your drive doesn’t work.

External hard drives are the same as internal hard drives except they are in an external enclosure, this enclosure isn’t only to protect the drive it also has a data transfer interface and power input port. If the connector type can meet the requirements to supply both the power and the information then these two things can be combined into one connection like USB – C.

Where internal hard drives can expect to receive a minimum regulated power supply and standard SATA or PCB connections, external hard drives have numerous connection possibilities that are continuously evolving and offer various amounts of voltage.

3.5″ drives will require 12v so will need to use an interface or combination of power and data transfer interfaces that can offer that. This is why it is important to use the cables that came with your hard drive or with a certified alternative. If your drive uses USB – C to both powers the drive and to transfer the data, a cable that doesn’t have that capability will mean that your drive simply won’t work. For example, a USB – 2.0 cable with USB- C adapters won’t be able to power a USB – C drive.

How to tell what voltage your hard drive requires.

The simplest way to tell is to search online or in the documentation that came with your hard drive for the specifications. This will inform you exactly.

That said there are other ways to tell, although you won’t be able to confirm definitely without the manufacturer’s spec.

Is the drive internal or external?

Internal drives – 3.5″ drives are typically 12v and 2.5″ drives are typically 5v. Laptops use 2.5″ drives, desktops can use both. Use system information to find the model number of your drive to cross-reference the specs online.

External drives – the same thing applies 2.5″ = 5v, 3.5″ = 12v. If you are unsure which is which check the following, if the hard drive requires a plug to the mains then it is 12v, if it uses power from the device then it could be either so it depends whether the device uses a connector that can offer 12v, if it doesn’t then it is 5v. If it does then you need to check whether the drive is 2.5″ or 3.5″, google searches the make and model to be sure.

What physical size is the drive?

The easiest way to tell is to know whether you have a 2.5″ drive or a 3.5″ drive. Here is the difference…

As you can see one is much smaller than the other, the measurement in the name refers to the width.

What type of storage is the drive?

HDDs have been outlined above, flash drives (USB sticks and memory cards) typically require 5v and SATA SSDs typically use 5v as well.

What connections does it require?

If it has a power port as well as a data port it will likely use 12v. If it only requires one cable it depends on the connection itself and what voltage that connection will support. But note a connection that can provide 12v doesn’t mean it uses 12v, it could still use 5v.

Does a particular voltage drive work better than another?

The voltage doesn’t dictate the power consumption alone meaning that both could provide the same spindle speed so long as the input could cope with the higher current required from a 5v supply. You would need to know the current that the drive draws and wattage to calculate its efficiency.

It also depends on function, a 3.5″ drive requires more power than a 2.5″ drive but it has more capacity for higher amperage meaning a higher-performing drive. This is only true for HDDs


There are many reasons why a hard drive might be 5v or 12v and whether that matters to you depends on your needs and the function of the hard drive as a storage solution. Internally your computer will take care of things for you, but externally a drive that requires a power source might be handy or a hindrance, it depends on your individual needs.

No matter what you need, we’ve said it before and we’ll say it again, and again, and again….. BACKUP YOUR HARD DRIVES!!!!!