Which convention should I use for a historian estimate?

Estimate in bytes, then convert once at the end. Mixing conventions midway through a sizing exercise is where the error creeps in.

PLC & Data

Data Size Converter

Convert between bytes, kilobytes, megabytes, and gigabytes in both the decimal and binary conventions, which differ by a growing margin.

Read before using this calculator

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Calculated reference results

Bytes: 1,000,000,000
Bits: 8,000,000,000
Kilobytes (1000): 1,000,000KB
Megabytes (1000): 1,000.00MB
Gigabytes (1000): 1.00000GB
Terabytes (1000): 0.00100000TB
Kibibytes (1024): 976,563KiB
Mebibytes (1024): 953.674MiB
Gibibytes (1024): 0.931323GiB
Tebibytes (1024): 0.000909495TiB
Modbus registers to hold this: 500,000,000

The arithmetic

1.0000 GB = 1,000,000,000 bytes

What this does not account for

Storage vendors quote decimal units and operating systems commonly report binary units, which is why a drive sold as 1 TB appears as about 931 GB.
Network throughput is quoted in bits per second, not bytes. A 100 Mbps link moves at most about 12.5 megabytes per second before protocol overhead.

How this is calculated

Storage is quoted in two conventions. Decimal units use powers of 1000, so a megabyte is 1,000,000 bytes. Binary units use powers of 1024, so a mebibyte is 1,048,576 bytes. The gap grows with size: a decimal terabyte is about 9% smaller than a tebibyte, which is why a drive sold as 1 TB shows as roughly 931 GB.

Assumptions and limitations built into this calculator

Decimal units are powers of 1000 and binary units are powers of 1024, per IEC 80000-13.

Frequently asked questions

Which convention should I use for a historian estimate?: Estimate in bytes, then convert once at the end. Mixing conventions midway through a sizing exercise is where the error creeps in.

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Content on CurryControls.com is general technical reference information provided for educational and reference purposes only. It is not engineering advice for a specific installation. All information must be independently verified against current codes, standards, manufacturer documentation, project requirements, and qualified professional judgment before it is relied upon or applied.