Pixels, physical size, and PPI
Four measurements are often mixed together: pixel dimensions, physical print size, PPI, and file size. Pixels describe the image grid. Inches, millimetres, or centimetres describe the intended print area. PPI connects those two measurements, while KB or MB records how many bytes the encoded file occupies.
A quick calculation
A 1200 × 1800 pixel image can print at 4 × 6 inches at 300 PPI because 1200 ÷ 300 = 4 and 1800 ÷ 300 = 6. Changing only the PPI tag does not add pixels or detail. If a form asks for exact pixel dimensions, follow that rule directly instead of trying to reach it through PPI.
Screen-based uploads usually care about pixel width, pixel height, format, and byte size. Print services may also read density metadata. Check the receiving instructions before resampling an image that already has enough pixels.
Exact size versus maximum size
Read the upload rule literally. “Up to 250 KB” calls for a maximum: any verified file at or below the ceiling should pass that part of the check. A range such as “100–250 KB” needs both a floor and a ceiling. An instruction that says “approximately 200 KB” may justify an exact target.
Why exact bytes are unusual
Image encoders expose stepped quality and dimension controls, not a dial for every possible byte count. Exact Size Tools treats an exact image result as within ±2% of the target and reports the final byte count. If the receiving form only gives a maximum, maximum mode preserves more quality and avoids chasing a needlessly narrow number.
Choosing a format
JPG suits most photographs and produces broadly accepted, compact files. PNG is the safer choice for signatures, line art, screenshots, and anything that needs transparent pixels. WebP can be smaller, but use it only when the receiving service lists it as accepted. Converting transparency to JPG permanently fills those pixels with the background colour you choose.
Preserving results from online calculators
When a supporting document begins in another web tool, save the result directly when possible. For example, a grey-structure cost estimate or a rock and gravel quantity estimate is better printed or exported from the calculator than copied from a compressed screenshot. If an application specifically asks for an image, crop the screenshot to the relevant result and check that every number remains legible.
Final upload check
Open the downloaded file before submitting it. Confirm the dimensions, format, and byte count, then zoom in on faces, handwriting, small labels, and figures. Keep the original file until the receiving service has accepted the new version.