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Unit Conversions
Data Storage Converter — Bits, Bytes, KB, MB, GB & TB
MB to GB and back, plus the decimal-versus-binary difference that makes drives look smaller
Digital storage is measured in two number systems at once, and that is exactly why a "1 TB" drive shows up on your computer as about 931 GB. This converter moves any amount of data between the units you actually meet — bits and bytes, the decimal KB, MB, GB, TB and PB that marketers and the SI standard use, and the binary KiB, MiB, GiB and TiB that your operating system uses under the hood.
Everything is built on one fact: 1 byte = 8 bits, and a byte is the base unit here. From there, two different scaling rules exist:
- Decimal (SI) units multiply by 1000 each step: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 1,000,000,000 bytes, 1 TB = 1,000,000,000,000 bytes. This is what drive manufacturers, network speeds and most file sizes officially use.
- Binary (IEC) units multiply by 1024 each step: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes, 1 TiB = 1,099,511,627,776 bytes. Windows still labels these "GB," which is the root of the confusion.
Formula: bytes = value × (factor of the FROM unit), then result = bytes ÷ (factor of the TO unit).
Worked example — convert 500 MB to GB. First to bytes: 500 × 1,000,000 = 500,000,000 bytes. Then bytes to GB: 500,000,000 ÷ 1,000,000,000 = 0.5 GB. The decimal step between MB and GB is simply ÷ 1000.
The famous gap — why "1 TB" reads as ~931 GB. A 1 TB drive holds 1,000,000,000,000 bytes (decimal). Your OS divides by 1024 three times: 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB, which it mislabels as "GB." Nothing is missing — the same bytes are just being counted in 1024-sized chunks instead of 1000-sized ones.
The common mistake is mixing the two systems — treating 1 GB as 1024 MB, or assuming a 256 GB phone gives you a full 256 GiB. This tool keeps decimal and binary units separate and exact, so 1 GB = 1000 MB while 1 GiB = 1024 MiB, and you always know which one you're holding. Pick an amount, a from unit and a to unit, and you'll also get a table showing the same data size in every unit at once.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Base unit = byte; 1 byte = 8 bits. • Convert to bytes: bytes = value × (factor of the FROM unit) • Convert out: result = bytes ÷ (factor of the TO unit) • Decimal (SI): KB = 1000 B • MB = 1e6 B • GB = 1e9 B • TB = 1e12 B • PB = 1e15 B • Binary (IEC): KiB = 1024 B • MiB = 1,048,576 B • GiB = 1,073,741,824 B • TiB = 1,099,511,627,776 B
📰 Formula
• Base unit = byte; 1 byte = 8 bits. • Convert to bytes: bytes = value × (factor of the FROM unit) • Convert out: result = bytes ÷ (factor of the TO unit) • Decimal (SI): KB = 1000 B • MB = 1e6 B • GB = 1e9 B • TB = 1e12 B • PB = 1e15 B • Binary (IEC): KiB = 1024 B • MiB = 1,048,576 B • GiB = 1,073,741,824 B • TiB = 1,099,511,627,776 B
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Assuming 1 GB = 1024 MB. In decimal units 1 GB = 1000 MB; only the binary GiB equals 1024 MiB.
- Confusing bits and bytes — an 8-bit byte means an 800 Mbps link transfers about 100 MB per second, not 800.
- Mixing decimal and binary scales in one chain (e.g. KB then ÷1024 then ÷1000).
- Reading an OS 'GB' figure as decimal GB — it's almost always a GiB (1024-based) value.
- Forgetting capitalization: 'Mb' means megabit, 'MB' means megabyte (8× larger).
💡 Tips
- Lock in 1 byte = 8 bits and a single base — bytes — and every other conversion is one multiply and one divide.
- Use decimal units (KB/MB/GB) for drive sizes and network speeds; use binary units (KiB/MiB/GiB) to match what your OS reports.
- To go from a marketed GB to the GiB your OS shows, divide by 1.073741824 (≈ 7% smaller).
- When a number looks 'off by about 7% per step,' you're crossing the 1000-vs-1024 line.
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❓ Frequently asked questions
How many MB are in a GB?
In decimal (SI) units, 1 GB = 1,000 MB, since each step multiplies by 1000. Most file sizes, drive labels and network speeds use this convention. The binary equivalent, 1 GiB, equals 1,024 MiB instead.
How do I convert MB to GB?
Divide the number of megabytes by 1000. For example, 500 MB ÷ 1000 = 0.5 GB, and 2,500 MB ÷ 1000 = 2.5 GB. To go back from GB to MB, multiply by 1000.
Why does my 1 TB drive only show about 931 GB?
The drive truly holds 1 TB = 1,000,000,000,000 bytes (decimal). Your operating system divides by 1024 three times, giving 931.32 GiB, but labels it 'GB.' No space is lost — it's just counted in 1024-sized chunks.
What's the difference between GB and GiB?
A gigabyte (GB) is decimal: 1,000,000,000 bytes. A gibibyte (GiB) is binary: 1,073,741,824 bytes, about 7.4% larger. Manufacturers use GB; Windows shows GiB while calling it 'GB.'
How many bytes are in a kilobyte?
It depends on the system. A decimal kilobyte (KB) is exactly 1,000 bytes, while a binary kibibyte (KiB) is 1,024 bytes. This converter keeps both available so you can pick the right one.
What's the difference between bits and bytes?
1 byte = 8 bits. Storage is usually measured in bytes (MB, GB), while internet speeds are measured in bits (Mbps). An 800 Mbps connection delivers roughly 100 MB per second because you divide by 8.
Is a kilobit the same as a kilobyte?
No. A kilobit (Kb) is 1,000 bits, while a kilobyte (KB) is 1,000 bytes — eight times larger. Watch the case: lowercase 'b' is bits, uppercase 'B' is bytes, which matters most for download estimates.
How big is a petabyte?
A petabyte (PB) is 1,000 TB, or 1,000,000,000,000,000 bytes (10^15). It's the scale of large data centers; 1 PB could hold roughly 250 million high-resolution photos.
Are these conversion factors exact?
Yes. Decimal units are exact powers of 1000 and binary (IEC) units are exact powers of 1024, both fixed by international standards, so every result here matches the official definitions rather than a rounded estimate.