File Size Converter
Convert file sizes between all common units instantly — enter any value in Bytes, KB, MB, GB, TB or their binary equivalents (KiB, MiB, GiB, TiB) and all other units update in real time. All calculations run entirely in your browser — no data is sent to any server.
SI (Decimal) vs IEC (Binary) Units
The most common source of confusion with file sizes is the difference between decimal (SI) and binary (IEC) prefixes:
| Standard | Prefix | Factor | Example |
|---|---|---|---|
| Decimal (SI) | kilo / mega / giga | Powers of 1,000 | 1 GB = 1,000,000,000 B |
| Binary (IEC) | kibi / mebi / gibi | Powers of 1,024 | 1 GiB = 1,073,741,824 B |
Why does this matter? A “500 GB” hard drive uses the decimal standard, so it contains 500,000,000,000 bytes. But Windows (before Windows 10) would report this drive as ~465 GB because it used binary division — it was actually showing 465 GiB. The IEC introduced the KiB/MiB/GiB notation in 1998 to eliminate this ambiguity.
Bits vs Bytes
Network speeds are measured in bits per second (bps, Kbps, Mbps, Gbps), while file sizes use bytes:
- 1 byte = 8 bits
- 100 Mbps internet connection = 12.5 MB/s actual download speed
This is why a “100 Mbps” plan downloads large files at roughly 12 MB/s, not 100 MB/s.
Download Time Formula
Download time (seconds) = File size (bytes) ÷ Bandwidth (bytes/second)Where Bandwidth (bytes/s) = Mbps × 1,000,000 ÷ 8
Example: A 4K movie (25 GB) on a 500 Mbps connection:
- 500 Mbps = 62,500,000 bytes/s
- 25,000,000,000 ÷ 62,500,000 = 400 seconds (~6.7 minutes)
Common Unit Conversions
| From | To | Formula |
|---|---|---|
| MB → GB | ÷ 1,000 | 1500 MB = 1.5 GB |
| GB → MB | × 1,000 | 2.5 GB = 2,500 MB |
| MiB → GiB | ÷ 1,024 | 1,536 MiB = 1.5 GiB |
| MB → MiB | ÷ 1.048576 | 100 MB ≈ 95.37 MiB |
| GB → GiB | ÷ 1.073741824 | 1 GB ≈ 0.9313 GiB |
| Mbit → MB | ÷ 8 | 100 Mbit = 12.5 MB |
Which Units Does My OS Use?
- macOS (since Snow Leopard 10.6): Decimal SI — “1 GB” really means 1,000,000,000 bytes
- Windows 10+: Also decimal SI
- Windows 7/8 / Linux
df: Binary IEC — “1 GB” label on a 1,073,741,824 byte partition - Hard drive manufacturers: Always decimal SI
- RAM: Always binary (e.g. 8 GiB of RAM = 8,589,934,592 bytes)