How to keep a file inside a required KB or MB range

Before touching the file, write down three things from the instruction: the unit (KB or MB), the operator (“maximum”, “minimum”, or “between X and Y”), and whether the limit applies to a single file or to a group of files in one archive. All three are commonly misread, and each one changes the plan: a single maximum is easy, a two-sided range needs margin at both ends, and a group limit means budgeting across several files rather than solving one.

Limits are usually enforced by the receiving system, and systems differ on whether KB means 1000 or 1024 bytes. Treat the stated number as slightly stricter than it reads.

• **Images** — format first, then quality, then dimensions. Photographs compress dramatically when moved to JPEG or WebP and when quality drops from the camera's default. See how dimensions affect file size.
• **PDFs** — embedded images dominate. A PDF that is mostly scanned pages behaves like a folder of images bound together, while a text-and-vector PDF of the same page count can be a fraction of the size. See reducing a PDF while preserving readability.
• **Documents built from scratch** — invoices, price lists and forms generated by tools on this site are text and vector only, so they are already small; adding many images is what grows them.
• **Archives** — a ZIP of already-compressed JPEGs rarely gets smaller, because ZIP cannot re-compress what is already compressed. Compress the individual files first, then package.

1. 1Measure the starting point: check dimensions and byte size with Image Metadata (or open the file properties) so you know how far you are from the target.
2. 2Make the cheapest change first — format or quality — and re-measure. Do not combine three changes in one pass, or you will not know which one worked.
3. 3If you are still far off, reduce dimensions, re-measure, and check visually at 100% zoom.
4. 4When the range is tight or two-sided, hand the last stretch to a targeted tool: Exact KB Photo Compressor iterates against a target and tolerance for you.
5. 5Leave headroom: land at roughly 90% of a maximum and roughly 110% of a minimum, so small differences in how the receiver counts bytes cannot disqualify the file.
6. 6Verify the final file itself — not a preview of it — before uploading.

For a batch of images and scans with a maximum edge and quality, Assignment Compressor applies exactly that budget across every file at once and reports what each one came out at.

• **You are compressing the wrong object.** If the limit is on the whole submission, one large file is usually the culprit — sort by size and attack the biggest first.
• **The source has no detail to throw away.** A screenshot with tiny text, or a line drawing, needs its dimensions reduced rather than its quality lowered, or the content stops being usable.
• **The format is fighting you.** A photograph stored as PNG will often not reach the target at any quality. Convert first.
• **The limit may be genuinely too tight for the content.** If legibility would be destroyed, that is worth knowing before you submit — check whether the instruction allows a different format, a link, or a separate upload slot.