File Size Unit Converter (MB / MiB / GB / GiB)
Instantly convert byte counts between KB, KiB, MB, MiB, GB, GiB. For boundary-value testing and upload-limit calculation.
✅ 100% free, no signup, runs entirely in your browser
Byte (B)
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KB (1,000 B)
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KiB (1,024 B)
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MB (1,000,000 B)
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MiB (1,048,576 B)
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GB (10⁹ B)
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GiB (2³⁰ B)
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TB (10¹² B)
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📖 How to Use
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Enter a value and unitEnter a number in the input field and select the unit (B / KB / KiB / MB / MiB / GB / GiB) from the dropdown.
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Check all converted valuesConverted values for B, KB, KiB, MB, MiB, GB, GiB, and TB are shown at once. Handy for boundary testing or upload limit design.
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Verify the difference between SI (MB) and binary (MiB)1 MB = 1,000,000 B; 1 MiB = 1,048,576 B. Use this when the unit in your OS differs from the spec.
❓ FAQ
What is the difference between MB and MiB?
MB (megabyte) is the SI unit: 1,000,000 bytes. MiB (mebibyte) is the IEC unit: 1,048,576 bytes. Windows shows drive sizes in MiB, so a 1 TB drive appears as 931 GiB.
Why does my OS show a different GB than the spec?
Windows displays sizes in binary units (GiB) but labels them "GB". macOS 10.6+ uses SI units (GB). Storage makers advertise in SI, causing the "1 TB shows as 931 GB" discrepancy.
How many bytes in 1 GB?
1 GB (SI) = 1,000,000,000 bytes (10^9). 1 GiB = 1,073,741,824 bytes (2^30). When implementing upload limits, be explicit about which unit you use.