How many KB are there in 1 MB?

By the binary count used here and in Windows, 1,024. By the decimal count shown in search answers and on many phones, 1,000. The two differ by a little over 2 percent, which only matters when a file sits right on a limit.

Which is bigger, 500 KB or 1 MB?

1 MB, by roughly double: 500 KB is just under half a megabyte. So a form that accepts up to 1 MB will take a 500 KB picture, but a form capped at 500 KB will turn a 1 MB picture away.

Can it change a PDF from MB to KB?

No. It reads pictures only and always hands back a JPG. When the upload has to be a PDF, shrink the photo here first, then turn that JPG into a PDF with the Print to PDF or share option. The PDF usually weighs a little more than the picture inside it, so aim a few KB under the PDF limit.

My form gives pixel dimensions or a crop as well as KB. In which order?

Shape first, weight second. Set the width and height with the resize tool, or trim with the crop tool, then bring that file back here. Resizing after compressing saves the picture again and can push it back over the limit.

Can the result stay a PNG?

No. Hitting a chosen size depends on adjusting JPG quality, and PNG has no such dial, so the download is always a JPG. Any transparent area turns white during the change.

Does it shrink videos or animated GIFs?

Not videos. A GIF is accepted, but only its first frame is kept and saved as a still JPG, so the animation is lost.

MB to KB Converter: Shrink a Photo to the KB You Need

On paper, going from MB to KB is a single multiplication: one megabyte is 1,024 kilobytes, so a 3 MB photo is 3,072 KB. On an upload form the figure has to actually come down. A picture straight off a phone camera weighs 2 to 5 MB, and a box that says 50 KB or 100 KB wants something roughly twenty to a hundred times lighter.

This page does that second job. Type the limit printed in your instructions, pick KB or MB beside it, and the photo is saved again as a JPG that weighs no more than the number you gave. The box opens at 100 KB, so change it before pressing the button.

A person in a red jacket, seen from behind, holding a smartphone sideways to photograph a turquoise lake

How to use it

Look up the size rule in the form’s instructions and note whether it is given in KB or MB.
Add your photo above, type that number into the size box and tap the matching unit. For a band such as 20–50 KB, tick the minimum option as well and enter the lower figure.
Press Compress. The result card lists the new weight, the pixel size and how much lighter the file has become.
Save the JPG to your device and attach it to the form. If faces or writing look soft, use the highest figure the rules allow instead of a lower one.

MB to KB in numbers, and why two answers exist

Multiply by 1,024 to turn megabytes into kilobytes, and divide by 1,024 to go back. Half a megabyte is 512 KB, 2 MB is 2,048 KB and 5 MB is 5,120 KB. In the other direction, 100 KB is just under a tenth of a megabyte and 20 KB is about two hundredths. A kilobyte is in turn 1,024 bytes, which is the unit this tool really measures.

The answer box Google shows above the results for this search says 1 MB = 1,000 KB. That is the decimal reckoning, and many phones and Macs use it when they list file sizes, while Windows and this tool count in steps of 1,024. Away from a limit the gap is irrelevant; right at one it decides the outcome. A JPG of 51,000 bytes reads as 49.8 KB on this page and as 51 KB in a phone’s file list. When a portal refuses a file that looks fine, enter a slightly smaller figure, such as 48 for a 50 KB rule or 97 for a 100 KB rule, and the result passes by either count.

How far a 3 MB phone photo can go, and what it loses

We ran two phone-resolution photos of 11 and 12 megapixels, each about 2.4 MB, through this exact tool. At 1 MB and at 500 KB both kept every pixel; only the JPG quality was lowered. At 200 KB they came back about 2,600 to 2,800 pixels on the long side, at 100 KB about 1,850 to 1,950, at 50 KB about 1,250 to 1,300, and at 20 KB roughly 650 to 830. Down to 100 KB the gap between the two came only from their shape; at 50 KB and below, the one with more fine detail came out smaller, and a plain portrait against a wall would sit near the top of each range.

Fine texture goes first: loose hair, fabric weave, distant leaves and the faint grain every phone sensor adds. After that the pixel count drops. For a form neither loss matters much, because the picture is usually shown a few centimetres wide, and even the 20 KB copy is several hundred pixels across. What cannot be recovered is the original, so keep it and let the tool work on a copy. Camera details and GPS location are stripped from the new file. For the most common limits, the related tools on this page have the number already filled in.

Frequently asked questions

How many KB are there in 1 MB?: By the binary count used here and in Windows, 1,024. By the decimal count shown in search answers and on many phones, 1,000. The two differ by a little over 2 percent, which only matters when a file sits right on a limit.
Which is bigger, 500 KB or 1 MB?: 1 MB, by roughly double: 500 KB is just under half a megabyte. So a form that accepts up to 1 MB will take a 500 KB picture, but a form capped at 500 KB will turn a 1 MB picture away.
Can it change a PDF from MB to KB?: No. It reads pictures only and always hands back a JPG. When the upload has to be a PDF, shrink the photo here first, then turn that JPG into a PDF with the Print to PDF or share option. The PDF usually weighs a little more than the picture inside it, so aim a few KB under the PDF limit.
My form gives pixel dimensions or a crop as well as KB. In which order?: Shape first, weight second. Set the width and height with the resize tool, or trim with the crop tool, then bring that file back here. Resizing after compressing saves the picture again and can push it back over the limit.
Can the result stay a PNG?: No. Hitting a chosen size depends on adjusting JPG quality, and PNG has no such dial, so the download is always a JPG. Any transparent area turns white during the change.
Does it shrink videos or animated GIFs?: Not videos. A GIF is accepted, but only its first frame is kept and saved as a still JPG, so the animation is lost.