How Hard Disk Prices Ranks Drives and Deal Scores
Updated
As an Amazon Associate we earn from qualifying purchases.
Every ranking on Hard Disk Prices comes from two checkable rules, price per TB and a 0 to 100 deal score against comparable offers in today's snapshot, and no brand or seller pays for placement.
Where the prices come from
Product titles, prices, availability, and links come from Amazon's product API for Associates. The snapshot is refreshed daily, and every displayed price shows the date and time it was captured, in US Eastern time. Once a snapshot is too old, its prices are hidden: no price older than a day is ever shown. That limit follows the Amazon Associates license, which restricts how long price data may be displayed.
Hard Disk Prices keeps no price history and shows no price trends from its own snapshots. Every product link goes to Amazon, and the site earns from qualifying purchases as an Amazon Associate. No brand or seller pays for placement; the order in the table comes only from the rules on this page.
How price per TB is worked out
Price per TB is the ranking's core number. It divides the listing's total price by its total capacity in decimal terabytes, where 1 TB equals 1,000 GB. Shipping and tax are not included.
The calculation follows four rules:
- Multipacks count every drive in the pack: a 2-pack of 4TB drives counts as 8TB.
- Capacity and pack size are read from the listing title.
- Link speeds such as "6Gb/s" are ignored, so they are never mistaken for capacity.
- If a title can't be read with confidence, the row gets a "possible mismatch" badge and no deal score.
What the deal score means
The deal score runs from 0 to 100. A score of 50 means the offer costs the typical price per TB for comparable offers. Each 1% below the typical price adds 1 point and each 1% above removes 1 point, so the score stops at 0 and 100 when an offer is 50% above or below typical.
"Comparable" and "typical" have exact meanings:
- Comparable means the same kind of drive (internal hard drive, internal SSD, external drive, or enterprise SAS drive), the same media for external drives (SSD or hard drive), the same condition (new, renewed, or used), and the same capacity rounded to the nearest TB.
- Typical is the median price per TB of those comparable offers in the current snapshot. Only today's offers are compared; no past prices are used.
- If fewer than 5 comparable offers exist, the comparison widens to drives of similar size (half to double the capacity), then to all sizes. The label under the score says which group was used, for example "8TB HDD" or "external HDD of similar size".
- An offer needs at least one other comparable offer to get a score.
What we filter out
The table leaves out anything that would distort a price per TB comparison or mislead a buyer:
- Products that are not drives: enclosures, docks, adapters, diskless or pre-filled NAS boxes, USB flash and thumb drives, and mounting kits.
- Listings marked currently unavailable.
- Listings with an implausibly low price per TB, which are held for review instead of ranked.
- Wrong condition labels: a title that says renewed or used is never shown as new.
- Enterprise SAS drives are hidden from the main table by default because they need a SAS controller. Choosing "Enterprise SAS" or searching shows them.
What a ranking can't tell you
The ranking measures price per TB only. It does not measure reliability, speed, noise, or seller quality, so two drives with the same price per TB can be very different products.
It also does not certify compatibility with a NAS, PC, or console; check the device maker's compatibility list before buying. A low price per TB can belong to an SMR drive or to a renewed drive with a shorter seller warranty, and the buying guides explain what to check for each kind of drive.
FAQ
Do brands pay to be ranked higher?
No. The order in the table comes only from the price per TB and deal score rules on this page, and no brand or seller pays for placement. Hard Disk Prices earns from qualifying purchases as an Amazon Associate when readers follow product links, but that does not change how offers are ranked.
How often do prices update?
The snapshot is refreshed daily through Amazon's product API for Associates. Each displayed price shows the date and time it was captured, in US Eastern time, and once a snapshot is too old its prices are hidden, so no price older than a day is ever shown.
Why does a drive show "possible mismatch"?
The badge appears when the listing title can't be read with confidence, so the capacity or pack size may be wrong. Because the price per TB can't be trusted, the row gets no deal score. Check the listing itself before buying to confirm what you are getting.
Why don't I see enterprise SAS drives in the main table?
They are hidden by default because they need a SAS controller; a standard SATA controller won't run them. If your hardware supports them, choose "Enterprise SAS" or search for a model to show them. They follow the same price per TB and deal score rules as every other drive.