# Data storage converter

> Storage capacity is measured in two systems — SI decimal (powers of 1000) and binary/IEC (powers of 1024). This converter handles both and shows the full conversion table.

Convert between bits, bytes, kilobytes, megabytes, gigabytes, terabytes, and binary equivalents (KiB, MiB, GiB, TiB).

**Interactive version:** https://onlinecalculator.me/unit-converters/data-storage/
**Category:** Unit Converters

## How to use

1. Enter a **value**.
2. Pick the **source unit** (what you have).
3. Pick the **target unit** (what you want).
4. The result appears instantly, plus a full conversion table for every other unit.

## Two measurement systems

Storage capacity is measured in two different ways, and they disagree by 2–10% depending on the size:

| SI unit | Value | Binary unit | Value |
|---|---|---|---|
| 1 KB | 1,000 B | 1 KiB | 1,024 B |
| 1 MB | 1,000,000 B | 1 MiB | 1,048,576 B |
| 1 GB | 10⁹ B | 1 GiB | 2³⁰ B |
| 1 TB | 10¹² B | 1 TiB | 2⁴⁰ B |
| 1 PB | 10¹⁵ B | 1 PiB | 2⁵⁰ B |

**SI decimal** (KB, MB, GB) uses powers of 1,000 — the standard SI prefix meaning. Used by hard drive manufacturers, network speeds, and almost all storage marketing.

**Binary / IEC** (KiB, MiB, GiB) uses powers of 1,024. Used by operating systems (Windows, macOS, Linux file managers), RAM manufacturers, and low-level programming. The "i" stands for *binary*.

## Why a 1 TB drive shows as 931 GB

You buy a 1 TB hard drive. You plug it in. Windows says the capacity is 931 GB. Nothing is wrong — this is the SI-vs-binary disagreement:

- Marketing: 1 TB = 10¹² bytes = 1,000,000,000,000 bytes
- Windows: divides by 1,024³ and calls it "GB" even though it means GiB
- 10¹² / 2³⁰ = **931.3 GiB**

At terabyte scale the gap is almost 7%. At the petabyte scale it's nearly 11%.

## Worked examples

### Movie-sized file — 4 GB

- 4 GB = 4,000 MB = 4,000,000 KB = 4,000,000,000 bytes = **32,000,000,000 bits**
- In binary units: 4 GB ≈ **3.725 GiB**

### iPhone storage — 256 GB

- 256 GB (advertised) = 256,000,000,000 bytes
- In the phone's "Settings → About" screen: **238.4 GiB** *(divide by 2³⁰)*
- Real usable space is lower still after the OS reserves a few gigabytes.

## Notes

- **Bits vs. bytes** — network speeds are quoted in **bits per second** (Mbps, Gbps); file sizes in **bytes** (MB, GB). A 1 Gbps connection downloads at 125 MB/s, not 1 GB/s. Divide by 8.
- **Capital B = byte, lowercase b = bit.** Mbps ≠ MBps. A common source of confusion when reading internet speeds versus file sizes.
- **RAM** is typically sized in GiB (binary) because of how addressing works. Storage is typically sized in GB (decimal). The same "16 GB" label can mean either depending on the component.

## Frequently asked questions

### What is the difference between KB and KiB?

KB (kilobyte) = 1,000 bytes (SI decimal). KiB (kibibyte) = 1,024 bytes (binary/IEC). Hard drives use decimal KB; operating systems often display binary KiB, which causes apparent size discrepancies.

### How many bytes in a gigabyte?

1 GB = 1,000,000,000 bytes (10⁹). 1 GiB = 1,073,741,824 bytes (2³⁰). A 1 TB hard drive holds 1,000 GB but shows as roughly 931 GiB in Windows.

### What is a bit vs a byte?

A bit is the smallest unit of data — a 0 or 1. A byte is 8 bits and can represent 256 values (0–255).

### How big is a petabyte?

1 PB = 1,000 TB = 1,000,000 GB. At 1 Gbps download speed, downloading 1 PB would take about 93 days.

### How do I share my conversion?

Click "Share with my numbers" to copy a URL with your units and value.

## Sources

- [Byte — unit of digital information and its multiples](https://en.wikipedia.org/wiki/Byte) — Wikipedia
- [Prefixes for binary multiples (kibi, mebi, gibi)](https://physics.nist.gov/cuu/Units/binary.html) — NIST

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