KB and MB explained: how to read a file size
How KB and MB relate (1 MB = 1000 KB, and the 1024 KiB note), how to convert, and how to check a photo’s file size on Android, iPhone, Windows and Mac.
The basic units
File size is measured in bytes. A kilobyte (KB) is 1,000 bytes and a megabyte (MB) is 1,000 KB, or 1,000,000 bytes. A phone photo is often 2–5 MB, while forms commonly ask for photos in tens or low hundreds of KB.
The 1,024 note
Some software counts in units of 1,024 instead: 1 KiB is 1,024 bytes and 1 MiB is 1,024 KiB. Windows uses these units but labels them KB and MB, so the same file shows a slightly smaller number there. The difference is about 2.4% for KB and about 4.9% for MB.
Converting
To go from MB to KB, multiply by 1,000: 2 MB is 2,000 KB and 0.5 MB is 500 KB. To go from KB to MB, divide by 1,000: 250 KB is 0.25 MB. The converter at /kb-to-mb/ does this both ways.
Checking size on Android
Open the photo in your gallery app and look for Details or Info, usually under the ⋮ menu or by swiping up. In the Files app, the size is shown under each file name. Menus differ between phone brands, but the size is usually listed with the date and resolution.
Checking size on iPhone
In the Photos app, open the photo and tap the info button (i) or swipe up to see its details, which on recent iOS versions include the file size. For a downloaded file, open the Files app, long-press the file and choose Get Info.
Checking size on a computer
On Windows, right-click the file and choose Properties; use the Size line, not Size on disk. On a Mac, select the file and choose File → Get Info, which counts in 1,000s. Because Windows counts in 1,024s, a file can look slightly smaller there than on a Mac or a phone.
What PhotoSize does
PhotoSize treats your KB limit as N × 1,000 bytes, the stricter reading, so the file passes whichever way a form counts. The result shows the size in bytes as well as KB, so you can compare it with what the form reports.
Questions
How many KB is 1 MB?
1 MB is 1,000 KB. Software that counts in 1,024s, such as Windows, treats 1 MB as 1,024 KB; the precise names for those units are MiB and KiB.
Is 500 KB bigger than 1 MB?
No, 500 KB is half of 1 MB. 1 MB is 1,000 KB, so any size under 1,000 KB is smaller than 1 MB.
How do I check a photo’s size in KB on my phone?
Open the photo and view its Details or Info (swipe up or tap the ⋮ or i button). For downloaded files, the Files app shows the size under the file name or in Get Info on iPhone.
Updated 2026-11-06