SI / decimal — KB, MB, GB, TB. 1 KB = 1,000 bytes . Used by storage manufacturers, network speeds (Mbps, Gbps), and the SI standard since 1960. IEC / binary — KiB, MiB, GiB, TiB. 1 KiB = 1,024 bytes . The IEC introduced these in 1998 to disambiguate. Linux du with -h uses these, as does macOS Finder for memory.

Sizing a backup, an upload, or a Docker image and matching what a tool reports. Converting "150 Mbps" download speed to MB/s (divide by 8 — bits to bytes). Estimating cloud-storage cost when one provider quotes GB and another quotes GiB. Figuring out how much "1 GB" of email actually is on disk.

Hard drives use decimal. A "1 TB" drive holds 1,000,000,000,000 bytes ≈ 931 GiB. The OS isn't lying — the marketing is using the smaller unit. RAM uses binary. "8 GB RAM" is almost always 8 GiB (8,589,934,592 bytes). RAM is built in powers of two. Network speed is in bits, not bytes. 100 Mbps = 100 megabits per second = 12.5 MB/s peak. Your "100 Mbit fiber" doesn't download a 100 MB file in one second. Some tools are inconsistent. macOS Finder switched from binary (with KB labels) to decimal in 10.6, then mostly stayed there. Windows Explorer still uses binary with KB labels — confusing but unchanged. Browsers' Content-Length is bytes. Always exact, no SI/IEC ambiguity.

File Size Converter

Convert between bytes, KB, MB, GB, TB and the binary KiB, MiB, GiB, TiB. Decimal vs binary clearly distinguished.

Value

From

Result

Enter input above to see the result.

What is this for?

"How big is 4 GB?" depends on who's asking. Hard-drive manufacturers, network engineers, and SI-following standards mean 4,000,000,000 bytes (powers of 1000). Operating systems, RAM modules, and most file managers historically meant 4,294,967,296 bytes (powers of 1024). The two numbers are 7% apart at the gigabyte scale and 10% apart at the terabyte scale — enough to feel cheated when a "1 TB" drive shows up as "931 GiB" on your computer. This tool converts between both systems so you always know which you're looking at.

The two systems

SI / decimal — KB, MB, GB, TB. 1 KB = 1,000 bytes. Used by storage manufacturers, network speeds (Mbps, Gbps), and the SI standard since 1960.
IEC / binary — KiB, MiB, GiB, TiB. 1 KiB = 1,024 bytes. The IEC introduced these in 1998 to disambiguate. Linux du with -h uses these, as does macOS Finder for memory.

When to use it

Sizing a backup, an upload, or a Docker image and matching what a tool reports.
Converting "150 Mbps" download speed to MB/s (divide by 8 — bits to bytes).
Estimating cloud-storage cost when one provider quotes GB and another quotes GiB.
Figuring out how much "1 GB" of email actually is on disk.

Common gotchas

Hard drives use decimal. A "1 TB" drive holds 1,000,000,000,000 bytes ≈ 931 GiB. The OS isn't lying — the marketing is using the smaller unit.
RAM uses binary. "8 GB RAM" is almost always 8 GiB (8,589,934,592 bytes). RAM is built in powers of two.
Network speed is in bits, not bytes. 100 Mbps = 100 megabits per second = 12.5 MB/s peak. Your "100 Mbit fiber" doesn't download a 100 MB file in one second.
Some tools are inconsistent. macOS Finder switched from binary (with KB labels) to decimal in 10.6, then mostly stayed there. Windows Explorer still uses binary with KB labels — confusing but unchanged.
Browsers' Content-Length is bytes. Always exact, no SI/IEC ambiguity.