File Size Converter
Convert any data size into every common unit at once: decimal units (KB, MB, GB, TB) as used by drive makers and networks, binary units (KiB, MiB, GiB, TiB) as used by Windows and memory, and bits for connection speeds. The converter also explains the gap between advertised and displayed disk sizes, estimates transfer times at your connection speed, and can measure the total size of dropped files.
- Runs in your browser
- No sign-up
- Free to use
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How to use File Size Converter
- Enter a size and choose its unit.
- Read the value in every other unit.
- Enter your connection speed to see transfer times.
- Or drop files to measure their total size.
File Size Converter features
15 units
Decimal, binary and bit units side by side.
Exact bytes
The precise number of bytes for any input.
Disk size explained
How Windows displays decimal drive sizes.
Transfer time
Ideal and realistic times at your connection speed.
Measure files
Drop files to total their sizes; contents are not read.
Flexible input
Accepts 1.5, 1,5, 1,500 and scientific notation.
When to use File Size Converter
- Checking whether a file fits an upload or attachment limit.
- Understanding why a new hard drive shows less space than advertised.
- Estimating how long a backup or download will take.
- Converting cloud storage or bandwidth quotas between units.
File Size Converter FAQ
Is 1 MB 1,000 or 1,024 kilobytes?
Officially 1 MB is 1,000,000 bytes, and 1 MiB is 1,048,576 bytes. Many programs, including Windows, still show binary values with MB labels, which is the source of most confusion.
Why does my 1 TB drive show about 931 GB?
The drive holds 1,000,000,000,000 bytes. Windows divides by 1,024³ and labels the result GB, which gives about 931.
How do bits relate to bytes?
One byte is eight bits. Connection speeds are given in bits per second, so a 100 Mbit/s line moves at most 12.5 megabytes per second.
Why is the realistic transfer time longer?
Protocol overhead, Wi-Fi conditions and server limits usually reduce real throughput to around 70–90% of the nominal speed.
Are my dropped files uploaded or opened?
No. Only their sizes are read.
Which unit should I use?
Use decimal units for storage products and network speeds, and binary units when matching what operating systems and memory specifications report.
Decimal and binary units
Data sizes come in two families that share confusingly similar names. The decimal family follows the metric system: a kilobyte is 1,000 bytes, a megabyte a million and a gigabyte a billion. Storage manufacturers, network equipment and the International System of Units use these. The binary family is based on powers of two: a kibibyte is 1,024 bytes, a mebibyte 1,048,576 and a gibibyte 1,073,741,824. Computer memory is naturally sized in these.
The confusion comes from software that calculates in binary but labels in decimal. Windows shows a 1 TB drive as 931 GB because it divides by 1,024 three times and still writes GB. macOS and many Linux tools switched to decimal units years ago, which is why the same file can appear to have different sizes on different systems. The converter shows both families side by side and explains the Windows figure.
Bits are the third piece. Network speeds are quoted in bits per second, with the same decimal prefixes, so a 100 Mbit/s connection carries at most 12.5 megabytes per second. Transfer times are calculated from the size in bits divided by the speed, and a second estimate at 80% throughput reflects typical real-world overhead.
Input is forgiving: decimal points and decimal commas, thousands separators and scientific notation are all understood. The exact byte count is always shown, which is useful when an upload limit or quota is defined to the byte.
Dropping files onto the page reads only their sizes, adds them up and converts the total, without opening or uploading the files.