Data Storage Converter

Storage space has a way of shrinking faster than you expect it to. You buy a 1 TB hard drive, format it, and discover it shows up as 931 GB. You pay for a "100 GB" cloud storage plan and wonder exactly how much you can actually store. Your phone says a single RAW photo is 24.3 MB, but you thought photos were "only a few megabytes." These aren't glitches — they're the result of inconsistencies baked into how storage is marketed, measured, and reported, and understanding them saves real frustration.

The Standard Conversion Table

Using decimal (SI) prefixes — which is what storage manufacturers and most networking contexts use: 1 kilobyte (KB) = 1,000 bytes. 1 megabyte (MB) = 1,000,000 bytes. 1 gigabyte (GB) = 1,000,000,000 bytes. 1 terabyte (TB) = 1,000,000,000,000 bytes. 1 petabyte (PB) = 1,000,000,000,000,000 bytes.

Using binary (IEC) prefixes — which is what RAM, operating systems, and some storage utilities use: 1 kibibyte (KiB) = 1,024 bytes. 1 mebibyte (MiB) = 1,048,576 bytes. 1 gibibyte (GiB) = 1,073,741,824 bytes. 1 tebibyte (TiB) = 1,099,511,627,776 bytes.

The divergence grows as you scale up. At the kilobyte level it's only 2.4% difference. By the terabyte level it's about 9.95% — nearly 10%. And at the petabyte level, you're looking at a difference of about 12.6%.

Understanding File Sizes in the Real World

Knowing typical file sizes helps you sanity-check storage estimates. A plain text document: 10–100 KB. A Word document with formatting and images: 200 KB to 5 MB. An MP3 audio file (3–4 minutes at 128 kbps): about 3.5 MB. A high-quality FLAC audio file: 20–40 MB. A JPEG photo from a smartphone: 3–8 MB. A RAW photo from a professional camera: 20–50 MB. A 1080p movie file (H.264): 1–4 GB per hour. A 4K movie file: 7–20 GB per hour.

These aren't exact — they vary with content, compression settings, and codec choices. But they give you anchors for estimating. If someone tells you a 10-minute video is "only 50 KB," something is wrong — that's impossibly small for any video file. If they say it's "50 GB," that's impossibly large for 10 minutes of standard video. These sanity checks catch unit errors fast.

Bytes, Bits, and the Building Blocks

Everything stored on a computer comes down to bits — individual binary digits, each either 0 or 1. Eight bits form one byte. One byte is enough to store a single ASCII character. The word "hello" is 5 bytes. These tiny units are the foundation of every storage size you'll ever encounter, and the distinction between bits and bytes matters more than most people realize.

Storage capacity is measured in bytes. Transmission speed is measured in bits per second. This is the core asymmetry that trips people up constantly. When your internet provider says you have a 500 Mbps connection, that's 500 megabits per second. When your file manager says a file is 500 MB, that's 500 megabytes. Downloading that 500 MB file on a 500 Mbps connection doesn't take one second — it takes about 8 seconds, because there are 8 bits in a byte. The factor-of-8 difference is consistent and predictable once you know it's there.

A Practical Scenario: Planning a Backup System

Say you're a 36-year-old freelance photographer in Portland. You shoot RAW files averaging 28.4 MB each, plus JPEG previews at about 7.1 MB each. After a busy month, you've accumulated approximately 3,800 RAW files and 3,800 JPEGs. How much storage do you need to back everything up?

RAW files: 3,800 × 28.4 MB = 107,920 MB = 107.92 GB. JPEG files: 3,800 × 7.1 MB = 26,980 MB = 26.98 GB. Total: approximately 134.9 GB. You want at least 2 backup copies (following the 3-2-1 backup rule: 3 copies, 2 different media, 1 offsite), so you need about 270 GB of backup capacity minimum, not counting any overhead for future growth. A 512 GB external SSD handles this comfortably with room to add about 4 more months of similarly paced work.

But if you're buying cloud storage for the offsite copy, remember that 134.9 GB using the decimal definition might display differently in your backup software if it uses binary sizing. Your 134.9 GB of files might show as about 125.7 GiB in some tools. This kind of discrepancy is why backup systems sometimes seem to use slightly more or less space than expected.

Related Calculators

• Unit Converter
• Speed Converter
• Time Unit Converter

The Prefix Problem: Where 931 GB Comes From

Here's the thing that drives a lot of confusion: hard drive manufacturers and operating systems use different definitions of "giga." Hard drive manufacturers use the SI (metric) definition where 1 GB = exactly 1,000,000,000 bytes. But Windows, older versions of macOS, and some Linux tools use the binary definition where 1 GiB (gibibyte) = 1,073,741,824 bytes.

So a drive marketed as "1 TB" contains exactly 1,000,000,000,000 bytes — one trillion bytes. Your operating system divides that by 1,073,741,824 (the binary definition of a gigabyte) and reports 931.32 GB. Both numbers are accurate. They just use different definitions. The drive manufacturer didn't steal 68.68 GB from you — they just counted differently. And honestly, this confusion has generated millions of support tickets and complaints over the decades, which is why the IEC introduced explicit prefixes: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), tebibyte (TiB) — all specifically defined as binary powers.

Cloud Storage: What You're Actually Getting

Cloud storage pricing is quoted in gigabytes or terabytes, and providers universally use the decimal (1,000-based) definition. So a 100 GB iCloud or Google Drive plan gives you 100,000,000,000 bytes of space. Your operating system might report that as 93.1 GiB if it uses binary prefixes. But the actual capacity is the same — the number displayed depends on which definition the reporting tool uses.

Cloud providers also count storage differently for different content. Google Photos counts storage for photos and videos at "high quality" against your quota, but photos and videos at "original quality" use storage. Google One's 2 TB plan gives 2,000,000,000,000 bytes of combined Gmail, Drive, and Photos storage. Once you understand the decimal definition, the math is straightforward.

What catches people off guard is compression. Some cloud services compress stored data before counting it against your quota; others don't. Some count the raw file size; others count what they actually store after deduplication. Reading the fine print on storage policies is worth doing before you rely on any quota figure for planning purposes.

Practical Tips for Working with Storage Sizes

The most reliable approach when planning storage needs is to work in the same unit system throughout. Pick either decimal (GB, TB) or binary (GiB, TiB) and convert everything to that system before doing any math. Mixing decimal manufacturer specs with binary OS reporting mid-calculation is a reliable way to end up with wrong answers.

When estimating storage for a project, calculate the maximum likely size rather than the average. Storage never seems tight until it's suddenly full. If your estimate says you'll need 412 GB, budget for 600 GB — that extra headroom covers the files you forgot to account for, the temporary copies created during processing, and the growth that happens as the project evolves.

And if you're troubleshooting a "disk full" error on a drive that seems like it should have space, check whether hidden files, system caches, or deleted items in the Trash are consuming space that isn't visible in your regular file browser. On most systems, deleted files stay in a recycle bin or trash folder and continue occupying space until you empty it. This is one of the most common sources of confusion when a drive seems inexplicably full.