How to Convert File Sizes: Bytes, KB, MB, GB (2026)

Every digital file has a size measured in bytes. As files get larger, that number is expressed in kilobytes, megabytes, gigabytes, or terabytes to stay readable. Knowing how to move between these units helps you judge whether a file fits an email limit, a cloud quota, or a phone's storage — without guessing.

The Conversion Ladder

Each unit is exactly 1,000 times the previous one in the decimal (SI) system used by operating systems, apps, and most file-sharing services. The table below shows the multipliers and a practical file-size example for each unit.

How to Convert Manually

To convert down (bytes to KB, KB to MB, and so on), divide by 1,000 at each step. To convert up (MB to KB, KB to bytes), multiply by 1,000. For example, a 4.7 MB PDF equals 4,700 KB or 4,700,000 bytes. A 250 GB SSD holds 250,000 MB or 250,000,000 KB. The math is straightforward; the only error to avoid is mixing up the direction.

Note that some tools and operating systems still use the binary definition — where 1 KB = 1,024 bytes — so reported sizes can differ slightly from the decimal values above. For everyday estimation the difference is under 2.5% and rarely matters.

Common Size Limits to Know

Gmail and most webmail clients cap attachments at 25 MB. WhatsApp limits video shares to 16 MB (or 2 GB via the Documents option). Most cloud storage tiers measure quotas in GB. App store download limits over cellular hover around 200 MB. Keeping these benchmarks in mind makes it easy to decide on the fly whether a file needs to be compressed or split before sending.

Use the File Size Converter to convert any value instantly across bytes, KB, MB, GB, and TB without doing the arithmetic yourself.