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IT Calculator (Storage, Transfer, Uptime, RAID)

Convert storage units (SI GB vs IEC GiB), estimate transfer time from file size and line speed, turn an uptime percentage into allowed downtime, and size RAID arrays, all with the formula shown. Type values with units, like “1.5GB” or “100Mbps”.

On-device・No upload

Your files and input are processed only inside your browser on this device and are never uploaded to our servers.

A bare KB, MB or GB means
Decides whether a value written as “GB” is 10^9 or 2^30 bytes. Units that tell them apart, such as “GiB” or “Gbit”, are always taken literally. Bit units (bps, Mbit …) are always 1000-based.

How to use

  1. Under “A bare KB, MB or GB means”, choose 1000-based (SI) or 1024-based (IEC). Values with an unambiguous unit such as “GiB” are always taken literally.

  2. In “Size conversion”, type something like “1TB” to convert it to every bit, SI and IEC unit, with the formula on each row.

  3. In “Transfer time & bandwidth”, get the time from a file size and line speed, the bandwidth needed for a deadline, the data moved in a time, or convert monthly volume to average bandwidth. Use overhead (%) to adjust the effective speed.

  4. In “Uptime & SLA”, turn 99.9% into the allowed downtime per year, month, week and day, or combine components in series or parallel.

  5. In “RAID capacity”, enter level, disk count and size for usable capacity and survivable failures; “Bitrate & logs” sizes video files and log storage. Copy any result with its button.

What it does

SI and IEC kept apart

kB, MB, GB are 1000-based; KiB, MiB, GiB are 1024-based. Bits and bytes are told apart by letter case. When a bare “GB” is ambiguous you can switch the default, and the tool shows how it read your input.

The formula is always shown

Each result carries the expression with numbers, such as “8,000,000,000 bit ÷ (100,000,000 bit/s × 1) = 80 s”. Copy one row or all results.

Uptime done carefully

Choose a 365-day or 365.25-day year; a month is the year ÷ 12. Series and parallel layouts are computed from the probability of being down, so setups with many nines do not lose precision.

RAID levels side by side

For RAID 0 / 1 / 5 / 6 / 10, compare usable capacity and survivable failures for the same disks. RAID 10 separates failures always survived from the best case.

Typed the way you write it

Full-width digits, commas, “ギガバイト”, “1h30m” and “3 nines” are understood. Floating-point noise such as 0.1 + 0.2 is cleaned before display, and extreme values (zero, negative, huge) give clear errors.

Use cases

  • Check why the capacity of an HDD or SSD looks smaller in the OS
  • Estimate how long a large upload or backup takes at a given line speed
  • Work out the average bandwidth a monthly data volume needs
  • Check how many minutes a 99.95% SLA allows per month before signing
  • Compare RAID 5 / 6 / 10 to decide disk count and usable capacity
  • Estimate video file size from bitrate, or storage needed for log retention

Capability matrix

FeatureSupportNotes
Size conversion (bit / SI / IEC)SupportedUp to peta
Transfer time, bandwidth needed, data moved, monthly volume ⇄ bandwidthSupported—
Uptime ⇄ allowed downtime, series and parallel compositionSupportedFor multi-tier layouts, feed one result into the next calculation
RAID 0 / 1 / 5 / 6 / 10 usable capacity and fault toleranceSupported—
Video bitrate ⇄ file size, log storageSupported—
Exact protocol overhead (TCP, TLS, VPN and so on)PartialApproximated by the percentage you enter; values per link type are not looked up
Measuring your real connection speedNot supportedNo network requests are made; use a speed-test site
Subnet / CIDR math, date arithmetic, base conversionNot supportedUse the IP / subnet, date-time and encode / convert tools
RAID levels beyond 0 / 1 / 5 / 6 / 10 (50, 60, mixed-size disks)Not supported—

Limits & notes

  • Sizes are limited to 8×10^30 bit. Zero and negative values are rejected where they make no sense (such as a speed of 0).
  • Up to 1000 disks per array, all the same size; RAID 10 needs an even count.
  • Availability is 0–100%, copies of a component 1–1000, and up to 10 components. Days in a month are 1–366.
  • Transfer figures are theoretical values reduced by the overhead you enter; real speed depends on devices and the remote server.
  • Results are rounded to 12 significant digits. A bare “GB” follows the chosen base (1000-based by default).

Privacy & safety

Values you enter are calculated in your browser only. Nothing is sent to or stored on a server, and the inputs are not put in the URL.

FAQ

Why does a 1 TB drive show as 931 GB?
Drives are sold with 1 TB = 10^12 bytes (SI), while Windows divides by 2^30 and labels the result “GB” (really GiB). 10^12 ÷ 2^30 ≈ 931.32, so 1 TB reads as about 931 GB. Try it in “Size conversion”.
What is the difference between GB and GiB?
GB and MB are 1000-based (1 GB = 10^9 bytes); GiB and MiB are 1024-based (1 GiB = 2^30 bytes). The gap is about 7.4% at GB and about 10% at TB. RAM is usually 1024-based, storage and networks 1000-based.
How long does 1 GB take over a 100 Mbps line?
1 GB = 8×10^9 bit divided by 100×10^6 bit/s gives 80 seconds in theory. Real transfers lose some capacity to headers and retransmission; with 10% overhead it is about 89 seconds.
What is the difference between Mbps and MB/s?
Mbps is megabits per second and MB/s is megabytes per second. With 8 bits per byte, 100 Mbps is 12.5 MB/s. The tool tells them apart by letter case and the /s suffix.
How much downtime does 99.9% allow per year?
With a 365-day year it is 8 hours 45 minutes 36 seconds; with 365.25 days, 8 hours 45 minutes 57.6 seconds. Per month (year ÷ 12) it is 43 minutes 48 seconds and per week 10 minutes 4.8 seconds.
How is RAID 5 usable capacity calculated?
(number of disks − 1) × disk capacity. Four 4 TB disks give (4 − 1) × 4 TB = 12 TB and survive one failure. RAID 6 uses disks − 2 and RAID 10 uses disks ÷ 2.

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