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Real Disk Size Formula:
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The Real Disk Size calculation explains the difference between advertised storage capacity (using decimal/base-10 calculations) and actual usable space (using binary/base-2 calculations). This discrepancy occurs because manufacturers use 1000-based units while computers use 1024-based units.
The calculator uses the formula:
Where:
Explanation: The formula converts between decimal gigabytes (10^9 bytes) and binary gigabytes (2^30 bytes), accounting for the ~7.37% difference.
Details: Understanding this difference helps explain why a "1TB" drive shows up as about 931GB in your operating system. This is normal and expected, not a defect or missing space.
Tips: Enter the advertised size in GB (decimal) to calculate the real usable size in GB (binary). For example, a 1TB (1000GB) drive will show approximately 931GB of usable space.
Q1: Why is there a difference between advertised and real size?
A: Manufacturers use decimal (base-10) calculations (1GB = 1,000,000,000 bytes) while computers use binary (base-2) calculations (1GB = 1,073,741,824 bytes).
Q2: Is this missing space or a scam?
A: No, this is a mathematical difference in measurement systems, not missing space. Both measurements are technically correct but use different standards.
Q3: Does this apply to all storage devices?
A: Yes, this applies to HDDs, SSDs, USB drives, and other storage media. The difference becomes more noticeable with larger capacities.
Q4: Why don't manufacturers use binary measurements?
A: The decimal system is more familiar to most consumers and makes capacities appear slightly larger in marketing materials.
Q5: Can I get the full advertised space?
A: No, this is a fundamental difference in measurement systems. The "missing" space isn't actually missing - it's just measured differently.