Storage calculator

Estimate how much storage you need from what you actually keep, rather than guessing a number and discovering it was wrong six months later.

Why the recommendation is higher than your content

The planner targets about 70 percent occupancy rather than filling the drive, for two reasons.

Solid state drives slow noticeably as they fill. Most use a portion of their capacity as a fast write cache, and that region shrinks as the drive fills up. A drive above roughly 80 percent full writes markedly slower than the same drive half empty.

Drives also need free space to manage themselves. Wear levelling spreads writes across the memory cells so no single area fails early, and that requires somewhere to move data to. A drive with almost no free space cannot do this well, which affects both performance and service life.

Why a 1 TB drive shows as 931 GB

Drive manufacturers count in powers of ten, so a terabyte is 1,000,000,000,000 bytes. Operating systems count in powers of two, where a terabyte is 1,099,511,627,776 bytes. Dividing one by the other gives roughly 0.931.

Nothing is missing and nobody is being cheated; the two are using different definitions of the same word. But plan around the smaller figure, because that is what you will actually see.

One drive or two?

A single large NVMe drive is the simplest arrangement and usually the right one. It is fast, there is no decision about what lives where, and nothing to manage.

Splitting across two drives makes sense in three situations: when you need more total capacity than one affordable drive provides, when you have a large archive of files you rarely touch and a mechanical drive costs much less per terabyte, or when you want to separate your operating system from your data for easier reinstalls.

Before planning a second drive, check how many M.2 slots and SATA ports the motherboard actually has, and read its manual on lane sharing. On many boards, filling a second or third M.2 slot disables two SATA ports, because they share the same chipset lanes. The PC Builder flags this when it applies.

NVMe or SATA?

NVMe drives are several times faster than SATA in benchmarks. In everyday use the difference is far smaller than that gap suggests, because most tasks are not limited by sequential transfer speed.

Where it does show: moving large files, working with video, and loading very large game assets. Where it does not: booting, launching applications, and general desktop work, all of which feel much the same on either.

NVMe drives are now similar enough in price that there is rarely a reason to choose SATA for a new build, unless you need more drives than you have M.2 slots for.

This is not a backup plan

Capacity planning and backup are different problems. A second drive in the same machine protects you from one drive failing; it does not protect you from theft, fire, ransomware, or deleting something by accident and not noticing for a month.

Anything you would be upset to lose needs a copy somewhere else, ideally somewhere not in the same building. That is worth more than any amount of capacity in the machine itself.

Related reading: How to choose an SSD and NVMe versus SATA.