Synology drive space calculator software#

Other answers have addressed the historical reason for the difference, but it seems to me like you are asking about the difference according to the mathematics. In reality, however, it's exactly the same number of bytes the number is only expressed differently! If you do the math again, you will see that 3.638694607 * 2^40 = 4.000787030016 * 10^12, so you get the same storage capacity in the end. This is the binary prefix 3.6 'tebibytes', where the 'bi' indicates that it's a base-two quantity.

It also looks like a smaller quantity, because 3.639 is less than 4.001, and that is bad for marketing (who wants to buy a 3.6 TB drive when the manufacturer next door sells a 4.0 TB drive for the same price?). Our hard disk can store more than 4 * 10^12 bytes, so in SI terms, it is a 4 terabyte storage device. In powers of ten, 4,000,787,030,016 bytes is 4.000787030016 * 10^12 bytes, which rounds quite nicely with four significant digits, it rounds to 4.001 TB, for the SI definition of 'tera': 10^12.

But as jcbermu illustrated, we choose to do so in two different ways: in powers of ten, or powers of two. For that reason, we choose to represent this information in some other way. Of course, the number 4,000,787,030,016 is somewhat unwieldy. However, the bytes are still there, you just can't use them to store files, because they are needed to store the data that effectively allows you to store the files.) (In practice, you then lose some of that to the computer's bookkeeping information: file system, journal, partitioning, etc.

For example, a 4 TB drive might have 7,814,037,168 sectors of 512 bytes each, which works out to a storage capacity of 4,000,787,030,016 bytes. Usually in general purpose computing, it's expressed as bytes or some multiple of bytes, but if you start looking at for example memory ICs (integrated circuits, chips), you will see their memory capacity expressed in terms of accessible bits.Ī hard disk will store some specific number of bits or bytes which, for technical reasons, are addressed in terms of sectors. Why is it less? If I see for 1GB more storage capacity in powers of 2 than powers of 10.Ī storage media - any storage media - can store a specific number of accessible bits. Jcbermu's answer is good, but I want to approach this from a different angle.ġGB is 1,000,000,000 bytes (powers of 10) and 1,073,741,824 bytes (powers of 2), then: it shows less storage capacity (the powers of 2). The operating system is the one that uses the wrong notation.ĭrive manufacturers hide this issue with disclaimers and explanations that always lead to the conclusion that “actual formatted capacity may be less”. You bought a 100 gigabyte drive, which is equivalent to a 93 gibibyte drive. But, and this is the big but, the operating system will only report the drive as having a capacity of 93 GB (10^11)/(2^30). If you buy a 100 GB hard drive, the capacity is 100x10^9 or 10^11 bytes. A “megabyte” can mean either 1000000 bytes or 1048576 bytes.

Synology drive space calculator software#

This is the correspondence table: Notation Symbol Valueġ terabyte 1 TB 10^12 = 1000000000000 bytesġ tebibyte 1 TiB 2^40 = 1099511627776 bytesġ6 years later a lot of hardware and software vendors still refer to the base-2 units with their SI names. The new units also got corresponding symbols, so ‘10 kibibyte’ is now written as 10 KiB instead of 10 kB. A kilobyte must be now a kibibyte and so on. The new names were created by replacing the second syllable in the old name by ‘bi’ (referring to ‘2’). To solve the problem, in the year 2000 The International Electrotechnical Commission or IEC proposed a notation scheme for the units based in powers of 2 on the norm ISO/IEC 80000-13. come into conflict with the International System of Units (SI) standard where “1 kiloWatt” means 10^3 or 1000 Watts. In addition the prefixes 'kilo', 'mega', etc. Hardware producers decided the names in this way:Ģ^10 = 1024 and as it's almost 1000 then call it 1 KilobyteĢ^20 = 1048576 bytes and as it's almost 1000000 then call it 1 Megabyteįor the normal user it is nonsense and cumbersome. The historical reason of using powers of 2 is that memory and hard disk are accessed by the CPU using an address space composed of lines on binary code.