📁 File Size Calculator & Converter

Convert file sizes between all units instantly, calculate how many files fit in storage, and estimate image and video file sizes from resolution, bit depth, bitrate, and duration.

File Size Units and Storage Planning

BrainyCalculators editorial insight — unique to this tool

A 4K movie rip ~20 GB; RAW photo 25–40 MB each. Database backup sizing multiplies row count × average row width. Same binary/decimal ambiguity as Data Storage Converter — OS reports GiB, vendor labels GB.

When to use this calculator

Use for file and media storage estimates. For monthly cloud bill, use Storage Cost.

Not what you need? For download duration at your Mbps, use Internet Speed. For byte math with KiB/GiB detail, use Data Storage Converter.

Just converting KB, MB, GB, or GiB units?

This page estimates image/video project sizes and storage capacity. For decimal vs binary prefix conversion and bit-to-byte math, use the Data Storage Converter →

File Size Converter

File Size

Unit

Image Size Estimator (Uncompressed)

Width (px)

Height (px)

Bit Depth

Video File Size Estimator

Video Bitrate (Mbps)

Duration — Hours

Duration — Minutes

What is File Size (and When to Use This Tool)?

File size is the amount of digital storage a file occupies, measured in bytes and larger multiples (KB, MB, GB, TB). This calculator goes beyond simple unit conversion: it estimates uncompressed image sizes from resolution and bit depth, projects video file sizes from bitrate and duration, and shows how many files fit on a given storage device.

Use this page when planning a creative project — sizing an SD card for a photo shoot, estimating edit-drive space for a video deliverable, or checking whether an attachment exceeds an email limit. The built-in converter handles byte multiples using binary (1024-based) factors, which matches how most operating systems report on-disk sizes.

For pure storage-unit algebra — converting between decimal GB and binary GiB, bits vs bytes, or reconciling cloud invoice units — use the Data Storage Converter instead. That tool explicitly toggles SI decimal vs IEC binary prefixes and explains why a 1 TB drive formats to ~931 GiB in Windows.

How the File Size Calculator Works

Formula, assumptions, and calculation steps for this ai & tech tool.

Methodology

AI and technology calculators estimate usage, cost, bandwidth, storage, or SaaS metrics by combining unit rates with volume assumptions.

Calculation Steps

Enter token counts, storage, traffic, users, or usage volume.
Normalize units such as GB, TB, tokens, requests, or months.
Multiply by the selected rate or apply the SaaS metric formula.
Show monthly or per-use totals for comparison.

Assumptions and Limits

Vendor prices can change and should be verified before budgeting.
Taxes, free tiers, and committed-use discounts are included only if modeled.
Results are estimates for planning and comparison.

Frequently Asked Questions

What is the difference between GB and GiB?

GB (Gigabyte) in common usage = 1,000,000,000 bytes (powers of 10). GiB (Gibibyte) = 1,073,741,824 bytes (powers of 2). Windows shows drive sizes in GiB but calls them GB, which is why a 1TB drive shows as ~931 GB in Windows.

Why does my downloaded file size differ from what was advertised?

File size can be reported differently by the server vs what you see on disk. Also, some sizes are in SI units (powers of 10) while OS file systems use binary units (powers of 2), creating a ~7% discrepancy at 1 GB.

What is uncompressed image size vs actual file size?

Uncompressed size (Width × Height × Bytes per pixel) is the raw data size. JPEG typically compresses to 5-20% of uncompressed size. PNG is lossless but achieves 30-80% compression. RAW files are near uncompressed.

How do I calculate video file size?

File Size (GB) = Bitrate (Mbps) × Duration (seconds) ÷ 8,000. A 2-hour 4K film at 25 Mbps = 25 × 7200 ÷ 8000 = 22.5 GB. Add 10-20% for audio tracks.

How much storage do I need for photos?

A typical modern smartphone photo is 3-8 MB in JPEG. 1 GB holds about 200-300 photos. A 1 TB external drive stores about 125,000-330,000 photos. RAW photos from DSLRs are 20-45 MB each — 1 TB holds about 22,000-50,000 RAW files.

Real-World Applications

☁️

Cloud Storage Planning

Calculate how many photos, videos, or documents fit in a 100 GB or 1 TB cloud storage plan before paying for an upgrade.

📷

Camera SD Card Sizing

Estimate how many RAW images (20–50 MB each) or 4K video minutes fit on a 64 GB, 128 GB, or 256 GB memory card.

🎬

Video Production

Convert video bitrate and duration to file size to plan capture storage, edit drive space, and delivery file sizes.

💾

Backup Drive Sizing

Add up the total size of folders to back up and compare against available drive capacity to choose the right backup drive.

📧

Email Attachment Limits

Check whether an attachment exceeds the 25 MB Gmail limit or 10 MB Outlook limit before attempting to send.

🌐

Transfer Time Estimation

Calculate how long it takes to upload or download a file given your measured broadband speed in Mbps.

Common Mistakes

Confusing bits and bytes

Internet speeds are measured in megabits per second (Mbps), but file sizes are measured in megabytes (MB). 1 byte = 8 bits — a 100 Mbps connection downloads at ~12.5 MB/s.

Mixing SI and binary units

Hard drives are sold in SI gigabytes (1 GB = 10⁹ bytes), but Windows reports in binary gibibytes (1 GiB = 2³⁰ bytes) — a 1 TB drive appears as ~931 GB in Windows.

Forgetting file system overhead

File systems (FAT32, NTFS, ext4) reserve 5–15% of drive capacity for metadata and system files — a "256 GB" drive may only offer ~230 GB of usable space.

Treating compressed and uncompressed as equivalent

A JPEG photo is 5–10× smaller than the same image as a RAW file or uncompressed TIFF — always know whether you're working with compressed or uncompressed sizes.

Using megabits for file size estimates

Video bitrates are often quoted in Mbps (megabits) — divide by 8 to get MB/s when estimating file sizes from streaming or recording bitrates.

File Size Unit Reference (SI vs Binary)

SI Unit	SI Bytes	Binary Unit	Binary Bytes
Kilobyte (KB)	1,000	Kibibyte (KiB)	1,024
Megabyte (MB)	1,000,000	Mebibyte (MiB)	1,048,576
Gigabyte (GB)	1,000,000,000	Gibibyte (GiB)	1,073,741,824
Terabyte (TB)	1,000,000,000,000	Tebibyte (TiB)	1,099,511,627,776
Petabyte (PB)	10¹⁵	Pebibyte (PiB)	2⁵⁰

References

IEC 80000-13. Quantities and Units — Part 13: Information Science and Technology. IEC, 2008.
NIST. Definitions of the SI Units — Prefixes for Binary Multiples. NIST, 2022.
IEEE Std 1541-2002. IEEE Standard for Prefixes for Binary Multiples. IEEE, 2002.
Tanenbaum, Andrew S. Modern Operating Systems. Pearson, 2014.
Patterson, David A. and Hennessy, John L. Computer Organization and Design. Morgan Kaufmann, 2020.