Data Storage Converter guide
Convert file sizes, drive capacities, and bandwidth between decimal units (KB, MB, GB, TB), binary units (KiB, MiB, GiB, TiB), and bits, with every conversion shown at once.
Two systems with the same names
Storage units come in two flavors, and most confusion comes from mixing them. Decimal (SI) units go up by 1,000: 1 KB = 1,000 bytes, 1 MB = 1,000,000, 1 GB = 1,000,000,000. Binary (IEC) units go up by 1,024: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576, 1 GiB = 1,073,741,824.
The IEC introduced the KiB/MiB/GiB names in 1998 precisely to end the ambiguity. Drive manufacturers, macOS (since 10.6 in 2009), iOS, Android storage settings, and network speeds use decimal. RAM is always binary. Windows File Explorer uses binary math but still prints KB, MB, and GB, which is why the same file can show two different sizes on two computers.
The formula
Every conversion goes through bytes. Multiply your value by the size of the source unit in bytes, then divide by the size of the target unit in bytes. For decimal units the factor is 1000^n, for binary units 1024^n, where n is 1 for kilo, 2 for mega, 3 for giga, 4 for tera, and 5 for peta. For bits, divide the byte count by 1/8, or simply multiply bytes by 8.
The gap between the two systems grows with each step. At the kilo level it is 2.4%. At giga it is 7.4%. At tera it is 9.95%. At peta, more than 12%. That is why nobody noticed the difference with floppy disks and everybody notices it with terabyte drives.
Worked example: the "missing" space on a new drive
You buy a 1 TB SSD. The box is accurate: 1 TB is 1,000,000,000,000 bytes. Plug it into Windows and it reports 931 GB. Divide one trillion by 1,073,741,824 (bytes in a GiB) and you get 931.32. Windows is showing GiB with a GB label. Nothing is missing.
A 500 GB drive shows as 465.66 "GB" on Windows. A 256 GB phone shows 238.42 GiB of raw capacity before the operating system takes its share. On a Mac, the same 1 TB drive shows 1 TB (minus formatting overhead) because macOS counts in decimal. Set the tool to 1 TB and GiB to reproduce the Windows number.
Bits vs bytes: internet speed math
Internet plans are sold in megabits per second (Mbps). Files are measured in megabytes. A byte is 8 bits, so divide the advertised speed by 8 to get the most megabytes you can move per second. A 400 Mbps plan tops out at 50 MB/s. A gigabit plan (1,000 Mbps) tops out at 125 MB/s.
Download time is file size in megabits divided by speed in Mbps. A 5 GB game is 40,000 megabits. On a 100 Mbps connection, that is 400 seconds, or 6 minutes 40 seconds, in a perfect world. Add 5-10% for protocol overhead and Wi-Fi losses. The FCC's current US broadband benchmark is 100 Mbps down and 20 Mbps up.
Real-world sizes to sanity-check your numbers
A plain-text email: 5-20 KB. A 12-megapixel phone photo: roughly 1.5-2.5 MB as HEIC, 3-5 MB as JPEG. A minute of MP3 at 128 kbps: about 0.96 MB. A minute of 1080p video from a phone: 60-130 MB. A minute of 4K at 30 fps: about 170 MB in HEVC, around 350 MB in H.264, according to Apple's own camera settings.
Gmail caps attachments at 25 MB. Many US government and job-application portals cap uploads at 2-10 MB per file. If you are over a limit, the image compressor on this site can shrink a photo without leaving your browser.
Common mistakes
Mixing b and B. Mb is megabits, MB is megabytes, and the difference is a factor of 8. Networking gear uses lowercase b; storage uses uppercase B.
Assuming RAM and storage use the same math. A "16 GB" laptop has exactly 16 GiB (17,179,869,184 bytes) of memory, while its "512 GB" SSD has 512 billion bytes of storage. Different conventions, same laptop.
Rounding too early. Convert through bytes in one step. Converting TB to GB, rounding, then GB to GiB compounds errors when you are sizing servers or cloud storage bills.
Frequently asked questions
Is 1 KB 1,000 or 1,024 bytes?
Officially 1 KB is 1,000 bytes and 1 KiB (kibibyte) is 1,024 bytes, per the IEC standard from 1998. In practice Windows still labels 1,024-byte units as KB, while macOS, drive makers, and network speeds use 1,000. This converter shows both.
Why does my 1 TB drive only show 931 GB?
The drive holds 1,000,000,000,000 bytes (decimal). Windows divides by 1,024 three times and reports 931.32, but calls it GB when it is really GiB. No space is missing; it is two different units with the same name.
How many MB are in a GB?
1,000 MB in decimal units, or 1,024 MiB in a GiB. For file sizes on a Mac or a phone plan, use 1,000. For RAM, use 1,024: an 8 GB memory stick is exactly 8 GiB.
What is the difference between Mb and MB?
Lowercase b is bits, uppercase B is bytes, and 1 byte is 8 bits. Internet speeds are sold in megabits per second (Mbps), so a 400 Mbps plan downloads at most 50 MB per second before overhead.
How long will a file take to download?
Convert the file size to megabits, then divide by your speed in Mbps. A 5 GB game is 40,000 Mb, so on a 100 Mbps connection it takes at least 400 seconds, about 6 minutes 40 seconds. Real-world overhead adds 5-10%.
How many photos fit in 128 GB?
A 12-megapixel iPhone HEIC photo is about 1.5-2.5 MB, so roughly 50,000 photos in 128 GB of free space. JPEGs are about twice as large. 4K video at 30 fps uses about 170-350 MB per minute depending on codec.
Is my data kept private?
Everything runs in your browser. Nothing you enter is uploaded to a server or stored by us.