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Storage ToolsNo signupNo paywallInstant resultsUpdated 2026-08-02

Drive Capacity Decimal/Binary Converter

See why your 1TB drive shows 931GB — convert decimal vs binary capacity.

Local & private by design

All processing runs locally in your browser, no data uploaded to servers. Nothing you enter leaves this page — there is no backend, no tracking pixel, no third-party API call. Close the tab and the inputs are gone.
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Advertised
1 TB
Formatted
931 GB
Usable
931 GB
Where did the space go?
Nothing is actually missing. Vendors count in decimal (1 TB = 1000⁴ bytes); Windows counts in binary (1 GB = 1024³ bytes). A 1 TB drive shows about 931 GB in Windows — a 6.9% labeling difference, plus 0 GB reserved by the OS.

The 1TB drive that showed 931GB

"I bought a 1TB drive and Windows says it's 931GB. Where did 69GB go?" This is one of the most common storage confusions, and the answer is that no space is actually missing. Drive vendors use decimal units (1 TB = 1,000,000,000,000 bytes = 1000⁴). Windows uses binary units (1 GB = 1,073,741,824 bytes = 1024³). Divide the vendor's decimal bytes by Windows's binary definition and you get ~931 GB. Same bytes, different labels.

The Drive Capacity Decimal/Binary Converter converts between decimal (KB/MB/GB/TB) and binary (KiB/MiB/GiB/TiB) units, explains the gap between advertised and formatted capacity, and helps you read specs honestly. Runs locally, no signup.

How the tool works

The converter uses two base definitions:

  • Decimal (SI) — 1 KB = 1000 bytes, 1 MB = 1000², 1 GB = 1000³, 1 TB = 1000⁴. Used by drive vendors and macOS.
  • Binary (IEC) — 1 KiB = 1024 bytes, 1 MiB = 1024², 1 GiB = 1024³, 1 TiB = 1024⁴. Used by Windows (which labels GiB as "GB", causing the confusion).

The converter takes any capacity in one unit and computes the equivalent in the other. The gap is ~7.4% at the giga scale, ~9.95% at the tera scale — which is why a 1 TB drive shows as ~931 GB in Windows.

The tool also accounts for filesystem overhead, partition alignment, over-provisioning, and recovery partitions, all of which reduce usable space below the formatted number.

Step-by-step usage

  1. Enter your drive's advertised capacity (e.g., 1 TB) and the unit (decimal).
  2. Pick the target unit (binary, GiB).
  3. Read the converted capacity. 1 TB → ~931 GiB.
  4. Subtract filesystem overhead (~2–5%) for a realistic usable-space estimate.
  5. Cross-check format and health using the Drive Read/Write Performance Rater if the drive also feels slow.

Common hardware problems this tool solves

  • "Where did 69GB of my 1TB drive go?" — nowhere. Decimal vs binary labeling. The converter confirms the math.
  • "My Mac shows more space than my Windows PC for the same drive" — macOS reports decimal GB/TB (closer to the advertised number); Windows reports binary. Same drive, different labeling.
  • "My drive shows even less after formatting" — filesystem overhead, partition alignment, OPAL/over-provisioning, and recovery partitions all reduce usable space below the formatted number.
  • "Is GiB the same as GB?" — no. 1 GiB = 1024³ bytes (binary); 1 GB = 1000³ bytes (decimal). The difference is ~7.4% at the giga scale.

For deeper storage context, browse the SSD fix hub.

Pro tips for storage buyers

  • The "missing" space is not missing. Decimal vs binary labeling accounts for the entire gap. Vendors are not cheating you on this one.
  • Plan for filesystem overhead too. NTFS, exFAT, APFS — each takes 2–5% for metadata and journaling. A 1 TB drive gives you ~900 GB usable after formatting.
  • Over-provisioning trades capacity for endurance. Leaving 10% of an SSD unallocated extends its life by giving the controller more spare blocks for wear leveling.
  • Recovery partitions eat space. Prebuilt PCs and laptops often ship with a 10–20 GB recovery partition. Back it up and reclaim it if you need the space.
  • macOS and Windows disagree on labels. Same drive, different numbers. Do not panic when the totals do not match across OSes.

Capacity is a labeling question, not a cheating question. The converter exists so you read specs honestly and plan storage with realistic numbers.

Drive Capacity Decimal/Binary Converter — FAQ

Why does my 1TB drive show 931GB?▾
Vendors use decimal (1 TB = 1000⁴ bytes); Windows uses binary (1 GB = 1024³ bytes). 1,000,000,000,000 bytes ÷ 1024³ = ~931 GB. No space is actually missing.
Is GiB the same as GB?▾
No — 1 GiB = 1024³ bytes (binary), 1 GB = 1000³ bytes (decimal). The difference is ~7.4% at the giga scale.
Where else does capacity go besides formatting?▾
Filesystem overhead, partition alignment, OPAL/over-provisioning and recovery partitions all reduce usable space below the formatted number.
Do Macs show the same number as Windows?▾
No — macOS reports decimal GB/TB (closer to the advertised number), Windows reports binary. Same drive, different labeling.
Are these hardware tools free to use?▾
Yes — every tool on TweakGearPro is 100% free, requires no account, and runs entirely in your browser. Nothing is uploaded to a server.
Do these tools work offline or send my data anywhere?▾
All processing runs locally in your browser, no data uploaded to servers. Once the page loads, the calculator works without a network connection.
Can I print or save my results?▾
Yes. Each tool has a "Print results" button that opens your browser print dialog, where you can save to PDF. Print styling hides navigation and side panels automatically.
Are the estimates accurate for my specific hardware?▾
They model typical real-world scaling across tiers, not any single SKU. Treat results as a planning baseline and always cross-check critical decisions against vendor specs and your own benchmarks.
Do the tools work on mobile?▾
Yes. Every tool stacks vertically on phones with touch-friendly inputs. Complex tables stay readable and scroll horizontally when needed.

Cross-site hardware resources

GameFixPro — Game FPS & Hardware TuningGame-side frame-rate fixes and hardware适配 guides.DevFixPro — Driver & System Error RepairDriver crash, BSOD and system error troubleshooting.