How to use the file size converter (kb/mb/gb)
- Enter the numeric size of your file or storage capacity.
- Select the source unit from the dropdown (B, KB, MB, GB, TB or PB).
- Choose the standard: binary (base-1024) for operating systems, or decimal (base-1000) for drive manufacturers and network speeds.
- Read the converted values across all units in the results table below.
How the math works
This gigabyte megabyte converter first translates your input into bytes, then divides by the target unit factor. In the binary system each step multiplies by 1,024. For example, converting 3 GB to MB: 3 x 1,024 = 3,072 MB. In the decimal system each step multiplies by 1,000, so 3 GB becomes 3 x 1,000 = 3,000 MB.
The byte counts for binary are: KB = 1,024, MB = 1,048,576, GB = 1,073,741,824, TB = 1,099,511,627,776, PB = 1,125,899,906,842,624. For decimal they are powers of ten: 103, 106, 109, 1012, 1015.
Binary versus decimal: why your drive looks smaller
Hard drive and SSD manufacturers label capacities using the decimal system, where 1 GB equals exactly 1,000,000,000 bytes. Windows and many operating systems report sizes using the binary system, where 1 GB equals 1,073,741,824 bytes. That gap explains why a "1 TB" drive shows up as roughly 931 GB in Windows.
To avoid confusion, the International Electrotechnical Commission introduced binary prefixes: KiB, MiB, GiB, TiB. However, most consumer software still writes "KB", "MB" and "GB" when it actually means the 1,024-based units. When you use this file size converter, pick the standard that matches your context.
Common file size reference table
The table below lists typical digital items and their approximate sizes. Use these as a starting point when estimating storage needs or download times.
| Item | Typical size |
|---|---|
| Plain text email | 20 KB |
| Smartphone photo (JPEG) | 3 to 5 MB |
| MP3 song (4 min, 320 kbps) | 9 to 10 MB |
| HD movie (1080p, 2 hours) | 4 to 6 GB |
| Modern AAA video game | 50 to 150 GB |
| Single-layer DVD | 4.7 GB (decimal) |
Practical uses for a file size converter
Knowing how to move between units helps in several everyday situations:
- Storage planning: figure out how many photos or videos fit on a USB stick or cloud plan.
- Download estimates: divide a file's size in megabytes by your connection speed in megabits per second (remembering 1 byte = 8 bits) to estimate transfer time. Tools like the data rate converter can help with bandwidth math.
- Server administration: log files and database dumps are often reported in mixed units; quick conversion prevents quota surprises.
- Comparing specs: phone spec sheets may list RAM in GB (binary) but internal storage marketing in GB (decimal).
Common mistakes to avoid
The most frequent error is mixing up bits and bytes. Network speeds are quoted in bits per second (Mbps), while file sizes use bytes (MB). One byte equals eight bits, so a 100 Mbps connection transfers at most 12.5 MB per second under ideal conditions.
Another pitfall is assuming every platform uses the same base. macOS since version 10.6 reports file sizes in decimal (base-1000), matching drive labels. Linux tools vary: ls -lh uses binary, while df -H uses decimal. Always verify which standard your tool applies before comparing numbers from different sources.
Worked examples
Each result below was produced by the same code the tool runs, so you can check your own numbers against them.
| Example | Input | Result |
|---|---|---|
| 1 GB to MB (binary) | Size: 1; From unit: GB; Standard: binary | Gigabytes (GB): 1; Bytes (B): 1,073,741,824; Kilobytes (KB): 1,048,576; Megabytes (MB): 1,024; Terabytes (TB): 0.000977; Petabytes (PB): 0.000001 |
| 4.7 GB DVD (decimal) | Size: 4.7; From unit: GB; Standard: decimal | Gigabytes (GB): 4.7; Bytes (B): 4,700,000,000; Kilobytes (KB): 4,700,000; Megabytes (MB): 4,700; Terabytes (TB): 0.0047; Petabytes (PB): 0.000005 |
| 500 MB to GB (binary) | Size: 500; From unit: MB; Standard: binary | Megabytes (MB): 500; Bytes (B): 524,288,000; Kilobytes (KB): 512,000; Gigabytes (GB): 0.488281; Terabytes (TB): 0.000477; Petabytes (PB): 0 |
| 1 TB drive (decimal) | Size: 1; From unit: TB; Standard: decimal | Terabytes (TB): 1; Bytes (B): 1,000,000,000,000; Kilobytes (KB): 1,000,000,000; Megabytes (MB): 1,000,000; Gigabytes (GB): 1,000; Petabytes (PB): 0.001 |
FAQ
How many megabytes are in a gigabyte?
In the binary system used by most operating systems, 1 GB equals 1,024 MB. In the decimal system used by drive manufacturers, 1 GB equals 1,000 MB.
Why does my 1 TB hard drive show only 931 GB in Windows?
The manufacturer defines 1 TB as 1,000,000,000,000 bytes (decimal). Windows divides that by 1,073,741,824 (the binary definition of a GB), yielding about 931.32 GB.
What is the difference between MB and MiB?
MiB (mebibyte) always means 1,048,576 bytes (base-1024). MB (megabyte) officially means 1,000,000 bytes (base-1000), though many programs still use MB to mean the binary value.
Is this gigabyte megabyte converter safe to use?
Yes. All calculations happen locally in your browser. No file sizes or other data are sent to any server.
How do I convert megabits to megabytes?
Divide the number of megabits by 8. For example, 100 megabits equals 12.5 megabytes.
Which standard should I choose for network speeds?
Network speeds are typically measured in decimal bits per second, but when converting to file sizes in bytes you will usually want the decimal option in this tool to stay consistent.