Softonic

File Size Analyzer

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Type a size in bytes and see it in every common unit: bytes, kilobytes (both KB = 1000 and KiB = 1024), megabytes and gigabytes. Handy for checking attachment limits, planning uploads and spotting that 450 MB attachment someone is about to email.

How to check a file size

  1. 1

    Enter the byte count

    Type or paste the size in bytes, for example 1048576 for 1 MiB.

  2. 2

    Read the unit breakdown

    See the exact byte count plus decimal (KB, MB, GB) and binary (KiB, MiB) conversions.

  3. 3

    Copy the value

    Copy the size in the unit you need, formatted for a report or a ticket.

KB vs KiB: the unit war

Unit Definition Used by
KB 1,000 bytes Disk vendors, SI standards, network speeds
KiB 1,024 bytes OS-level RAM reporting, file managers
MB 1,000,000 bytes Disk vendors, downloads
MiB 1,048,576 bytes Memory, Linux ls -h, RAM sticks
GB 1,000,000,000 bytes Disk, SSD, cloud quotas
GiB 1,073,741,824 bytes free -h, virtual memory

This is why a “1 TB” drive shows up as ~930 GiB in the OS, the drive is 10^12 bytes, but the OS counts in 2^30.

Transfer time reference (1 GB file)

Link speed Real throughput (~80%) Time for 1 GB
10 Mbps ~1.0 MB/s ~17 minutes
100 Mbps ~10 MB/s ~100 seconds
1 Gbps ~100 MB/s ~10 seconds
10 Gbps LAN ~1 GB/s ~1 second
Cellular 4G LTE ~2 MB/s ~8 minutes
Cellular 5G mid ~15 MB/s ~65 seconds

Real networks rarely hit the theoretical maximum; the estimates use 80% overhead by default.

Common mistakes

  • Mbps vs MB/s. 100 Mbps is 12.5 MB/s, not 100 MB/s. Divide the Mbps figure by 8 (plus overhead) to get real transfer rate.
  • Bytes vs bits. Disks are sold in bytes, network speeds in bits. Always check the unit on the datasheet.
  • Assuming “1 MB limit” is decimal. Some mail servers use 1,000,000 bytes, others 1,048,576. A 999,999 byte attachment is safe everywhere; 1,048,577 might bounce from one provider and not another.

Frequently Asked Questions

The drive really is 1,000,000,000,000 bytes (1 TB decimal), but the OS counts in binary, and 1,000,000,000,000 bytes is about 931 GiB. Vendors use decimal because the numbers are bigger.

No. Type the size in bytes directly and the breakdown appears instantly. This tool has no file upload.

TCP, routing and protocol overhead eat into the raw link speed. We assume real throughput is about 80% of theoretical; your mileage varies with latency, server, and ISP.

No, the input is a plain number of bytes, for example 1048576 for 1 MiB or 838860800 for 800 MiB. If you type “450 MB”, the letters are ignored and the tool reads it as 450 bytes, so always enter the byte count.

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