File Size Calculator — Calculate File Sizes Easily

Quickly convert & format file sizes between bytes, KB, MB, GB and TB. Supports bulk input and both 1000 & 1024 bases.

Tool

Use binary base (1024)

Convert to:

Precision:

Input (one value per line). Examples: 1024, 1.5 MB, photo.jpg 2.3GB

Output (results)

What is this tool?

A lightweight file size calculator that parses numeric values and common unit suffixes, converts them across units, supports bulk processing, and formats human-friendly output.

Convert between Bytes, KB, MB, GB and TB
Choose binary (1024) or decimal (1000) base
Bulk input: one entry per line (file names allowed)
Beautify and validate inputs with helpful messages
Accessible and responsive UI with copy-ready output

How to use

Paste or type values into the Input area (one per line).
Pick your target unit and precision; toggle binary if you want 1024-based results.
Click Convert to produce results in the Output area.
Use Beautify Output to add separators and align numbers; Validate Input checks for parse errors.
Copy or download the output for reports or scripts.

Real-world Use Cases

Estimating backup sizes for servers or cloud storage
Converting file lists produced by scripts for reporting
Verifying uploaded file sizes when preparing media
Quick conversions during QA or dev tasks

Benefits

Fast conversions — bulk-friendly
Precise control over base (1000 vs 1024) and decimals
Clean, copy-ready output and error guidance
No external libraries — lightweight and embeddable

FAQ

Q: Does it support both 1000 and 1024 bases?: A: Yes — toggle “Use binary base (1024)” to switch between SI (1000) and binary (1024) conversions.
Q: What input formats are accepted?: Numeric values (e.g., 1024), values with unit suffixes (e.g., 1.5 MB), or lines containing a filename and size (e.g., photo.jpg 2.3GB).
Q: Can I convert multiple values at once?: Yes — put each value on its own line and click Convert. Output will preserve line order.
Q: What precision does the tool show?: Choose decimal precision (0–8). The default is 3 decimal places. Beautify will add thousand separators for readability.
Q: Is the tool client-side only?: A: Yes — calculations happen in your browser; no data is sent to servers by this snippet (unless you embed additional code).
Q: Why do results sometimes differ slightly from other tools?: Because some tools use the decimal system (1000) while others use binary (1024). You can toggle the base here to match your reference.

Disclaimer

This tool is provided for informational use only. While it performs common file-size conversions and provides input validation, the authors are not liable for any inaccuracies or for decisions made based on its outputs. Always verify critical measurements when planning storage or backups.

How File Size Is Calculated

File size simply refers to the amount of digital space a file takes up on a storage device. It’s measured in units of data, and understanding these units helps explain why some files are small and others are very large.

At the most basic level, digital information is stored in bits (binary digits: 0s and 1s). Eight bits make up one byte, which is the standard unit used to measure file size. From there, sizes scale upward:

Kilobyte (KB) ≈ 1,024 bytes
Megabyte (MB) ≈ 1,024 KB
Gigabyte (GB) ≈ 1,024 MB
Terabyte (TB) ≈ 1,024 GB

This hierarchy shows how quickly file sizes can grow as more data is added.

Compression reduces file size by removing redundant information or encoding data more efficiently. For example, a ZIP file or JPEG image uses compression to shrink storage needs while keeping the content usable.

Different types of files vary in size because of the data they contain. Video files are typically much larger than images since they store thousands of frames, audio tracks, and metadata, while an image only stores a single frame.

File size also affects storage and bandwidth. Larger files take up more space on your hard drive or cloud storage, and they require more bandwidth to upload, download, or stream. That’s why optimizing file size is important for saving storage, speeding up transfers, and improving overall performance.