A 400KB ceiling is generous next to the 20KB and 50KB caps of exam forms, yet a straight-from-the-phone photo of 3 to 6MB is still ten times too heavy for it. The good news is that the gap can be closed almost entirely by storing the picture more efficiently, not by throwing pixels away, so the version you hand in can still fill a laptop screen.
The target here is locked at 400KB. Your photo is read on your own device, the quality is tuned until the weight fits, and the dimensions are trimmed only if tuning alone falls short. If the file is under 400KB to begin with, you are told so instead of getting a needlessly re-saved copy.
Before and after
2400 × 3600 px1.17 MBJPG
2400 × 3600 px399 KBJPG
This photo was 1.17 MB. With the limit set to 400 KB, it came out at 399 KB, which is 67% smaller.
The pixel size stayed at 2400 × 3600 px. Only the JPG quality was lowered.
The image on the right is the actual file the tool above produced.
How to use it
- Pick the oversized photo, scan or screenshot; HEIC, PNG, WebP and AVIF are read as well as JPG.
- Wait a moment while candidate qualities are encoded and weighed against the 409,600-byte ceiling.
- Read the result card: it lists the new weight, the width and height, and how much was saved.
- Save the JPG and attach it to the upload field that asked for 400KB.
How much picture fits in 400KB
Roughly two to three megapixels of a busy scene, which works out at about 2,000 to 2,500 pixels on the long side for an ordinary outdoor shot. Calm subjects such as a portrait against a wall, a document or a product on white keep more, often the full original size. A 12-megapixel phone photo usually loses a little resolution; a 4-megapixel one often loses none.
At that resolution the picture is wider than most monitors and holds enough for a print around 15 × 10 cm at photo-lab sharpness. Where you might notice a difference is when zooming deep into fine textures like hair or leaves; at normal viewing size the original and the 400KB copy are hard to tell apart.
Kilobytes, pixels and ranges
400KB describes how heavy the file is, not its shape. A request for 400 × 400 pixels is a different job, done with the resize tool, and such a square usually weighs far less than 400KB anyway. This page counts a kilobyte as 1,024 bytes, so the hard limit is 409,600 bytes and the output never goes over it.
Some instructions give a band, for example 300KB to 400KB, and turn away files that are too light. For those, tick “My form also has a minimum size” and type the lower number. The compressor then raises quality, and enlarges the picture if it has to, until the file sits between the two figures.
Frequently asked questions
- Will my photo lose quality at 400KB?
- Some data is always discarded when a JPG is made smaller, but at this budget the loss is rarely visible on a phone or computer screen. The tool picks the highest quality that still fits, rather than a fixed low setting.
- Can I get a 400KB PDF here?
- No, the output is a JPG image. If the upload asks for a PDF, make the JPG under 400KB first, then use your phone or computer’s print-to-PDF option; a PDF holding one such image weighs only slightly more than the picture itself.
- Why is my result 380KB and not exactly 400KB?
- Quality moves in steps, and the next step up would have crossed the limit. Landing a little under is expected; the byte count on the result card is the true size.
- My image is a PNG screenshot. Will text stay readable?
- Usually yes. A screenshot at its original resolution normally fits 400KB with room to spare, so the text keeps its sharpness. Any transparent areas turn white because the result is saved as JPG.
- Is location data kept in the compressed copy?
- No. Camera details and GPS position stored in the photo are stripped from the new file, and a phone shot taken sideways is saved the right way up.