ExactSize

Compress JPG to 100KB: what the upload form actually asks for

A 100 KB target is 102,400 bytes, and on the photograph used for this page that buys 1.3 to 1.6 million pixels — 1,594,957 from the uncropped 24-megapixel original, 1,510,706 from a 5:7 crop of it, 1,299,600 from a square crop. So the useful question is not "can I reach 100 KB" — you always can — but whether 100 KB holds the pixel size the form demands. At the smallest sizes real forms accept, it does with room to spare: 87% quality at 600 × 600, 84% at 600 × 750, 75% at 715 × 1000. At 1200 × 1200 it does not, and the compressor cuts the picture to 1140 × 1140.

Four numbers before you compress anything

  • None of the three official specs checked on 20 October 2026 caps at 100 KB. The UK passport asks for at least 50 KB and no more than 10 MB, New Zealand for 250 KB to 5 MB, Canada for 4 MB or less with no floor stated. If your form says 100 KB, it is stricter than all three.
  • One of them makes 100 KB ineligible. New Zealand's floor is 250 KB. Compressing a passport photo to 100 KB for that form produces a file it will not take — the constraint runs the other way.
  • 100 KB bites at the top of a pixel range, not the bottom. 600 × 600 was delivered at 87% quality with its dimensions intact; 900 × 1200 at 52%; 1200 × 1200 was cut to 1140 × 1140 and 2000 × 2800 to 1039 × 1454, both at the 40% floor.
  • If the form means 100,000 bytes, aim at 97 KB. Every output at a 100 KB target measured 100,825 to 102,384 bytes — right for 102,400, too big for 100,000. At 97 KB the same files came back at 85,669, 98,418 and 98,117 bytes.

All figures measured on 20 October 2026 with Chrome 155.0.8059.80 on Windows 11, driving this site's compressor. Same photograph, same session, one variable at a time.

How to read these numbers: one landscape photograph (Bachalpsee_reflection.jpg from Wikimedia Commons, 4000 × 6000) was centre-cropped to each pixel size below, resized with Lanczos and saved at JPEG quality 92, then fed in at a 100 KB target. Because every row is the same picture, the differences between rows come from the pixel size and the crop alone. Each row is one encode: these are sample points on one photograph, not a distribution across photographs. Every byte count and quality value is what the compressor printed in its own verdict line. This page is the form-requirement axis; the pure pixel-budget question at 100 KB for PNG files is on the PNG at 100 KB page.

Three official photo specs, read on 20 October 2026

These are the rules as written on the government pages themselves, not as summarised by a photo shop. The last column is what this compressor returned when the same photograph was prepared at the smallest pixel size that spec allows and given a 100 KB target.

Form Pixel rule, as written Byte rule, as written 100 KB at their smallest size
UK passport, digital photo
gov.uk/photos-for-passports		 at least 600 pixels wide and 750 pixels tall at least 50KB and no more than 10MB 600 × 750 kept, 100,825 bytes, 84% quality — inside the 50 KB floor
New Zealand passport
passports.govt.nz		 900–4500 pixels wide, 1200–6000 pixels high, 3:4 between 250KB and 5MB 900 × 1200 kept, 101,323 bytes, 52% quality — below the 250 KB floor
Canada, PR photo (IRCC guide 5291)
canada.ca		 between 715x1000 and 2000x2800 pixels file size must 4 MB or less 715 × 1000 kept, 101,619 bytes, 75% quality — inside 4 MB

Sources read directly on 20 October 2026. Canada's page also accepts PNG; the other two specify a photo, and the UK page additionally requires the picture to be unaltered by software, which is worth knowing before you touch the exposure.

Two things follow. First, 100 KB is not a number any of these forms asks for — the tightest ceiling among them is Canada's 4 MB, and the tightest floor is New Zealand's 250 KB. If a form you are filling in says "100 KB", it is a private system, a job portal or an exam registration, and its number is stricter than any passport office's. Second, the direction of the constraint matters. For the UK form a 100 KB file is fine and a 40 KB file is not; for the New Zealand form a 100 KB file is rejected outright. Compressing harder is not a safe default.

The US figure is missing on purpose. The State Department's photo page returned a bot challenge to every automated read on 20 October 2026, so the widely quoted "600 × 600 pixels, 240 KB" is not in the table. Only figures read on the page itself go in it.

One 100 KB target, six pixel sizes

The same photograph, cropped to each size and compressed once. The "kept" column is the share of the source's pixels that survived; anything under 100% means the compressor decided the pixel count had to give, because holding it would have pushed quality below its 40% floor.

Size fed in Source bytes Output at 100 KB Output px Output bytes Quality Kept
600 × 600 158,214 600 × 600 360,000 102,312 87% 100%
600 × 750 (UK minimum) 176,770 600 × 750 450,000 100,825 84% 100%
715 × 1000 (Canada minimum) 264,468 715 × 1000 715,000 101,619 75% 100%
900 × 1200 (NZ minimum) 401,091 900 × 1200 1,080,000 101,323 52% 100%
1200 × 1200 584,422 1140 × 1140 1,299,600 102,384 40% 90.3%
2000 × 2800 (Canada maximum) 1,736,969 1039 × 1454 1,510,706 101,686 40% 27.0%
4000 × 6000 (uncropped) 3,492,678 1031 × 1547 1,594,957 102,207 40% 6.6%

Measured 20 October 2026, Chrome 155.0.8059.80, Windows 11. Target set to 100 KB (102,400 bytes), format JPG. Source files were saved at JPEG quality 92 first, so no row starts from an already-compressed file.

Read the quality column as a budget: it says how much of the file went into the picture rather than into shrinking it. Between 600 × 600 and 900 × 1200 the dimensions never moved, and quality paid for the extra pixels — 87% down to 52%. Past 900 × 1200 the quality column hits its floor and the pixel count starts paying instead. That is the whole mechanism, and it is why "100 KB" has no single pixel answer.

The practical consequence for a form with a wide pixel range, like Canada's 715 × 1000 to 2000 × 2800: submit at the bottom of the range if 100 KB is your ceiling. 715 × 1000 kept every pixel at 75% quality. 2000 × 2800 lost 73% of its pixels and came back at 1039 × 1454 — the larger upload produced the smaller picture.

Why the same photo gets more expensive per pixel when you crop it

All three rows below sit at the compressor's 40% floor, so the bytes-per-pixel figure is comparable between them: output bytes divided by output pixels, same quality, same encoder. What changes is how much detail the frame contains.

Crop Output px Output bytes Bytes per pixel
Full frame, 4000 × 6000 1,594,957 102,207 0.064
5:7 crop, 2000 × 2800 1,510,706 101,686 0.067
Square centre crop, 1200 × 1200 1,299,600 102,384 0.079
Scanned page, 1200 × 1200 579,121 101,559 0.175

All four at the 40% quality floor, so this is a like-for-like comparison of encoder output, not a comparison of the source files' own compression.

The square crop costs 23% more per pixel than the full frame, because a square taken from the middle of a landscape throws away the sky and keeps the detail. That is why 1200 × 1200 — only 1.44 million pixels, fewer than the 1.59 million the uncropped file managed — still did not fit: at 0.079 bytes per pixel it would have needed about 113,000 bytes, and the compressor cut it to 1140 × 1140 instead of dropping quality below 40%.

The scanned page is the extreme case: 0.175 bytes per pixel, 2.7 times the photograph. A 1200 × 1200 scan came back at 761 × 761 at the same floor, while the photograph of identical pixel dimensions kept 1140 × 1140. If your upload is a document rather than a photo, 100 KB buys you 40% of the pixels — 579,121 against 1,440,000.

The 100 KB that isn't 100 KB

Every output in the table above landed between 100,825 and 102,384 bytes. All nine are under 102,400, which is what this tool means by 100 KB, and the verdict line said so each time: "100 KB is at or under your 100 KB target". But a form that writes "100 KB" and enforces 100,000 bytes — the decimal reading — would reject every single one of them, including the 100,825-byte file that looks the most compliant.

The difference between the two readings is 2.4%. On a small file that is the difference between accepted and rejected, and the fix costs almost nothing: aim lower than the number on the form.

File At 100 KB target At 97 KB target Quality 100 → 97 Output px 100 → 97
600 × 750 photo 100,825 B 85,669 B 84% → 83% 600 × 750 → 600 × 750
1200 × 1200 photo 102,384 B 98,418 B 40% → 40% 1140 × 1140 → 1120 × 1120
4000 × 6000 photo 102,207 B 98,117 B 40% → 40% 1031 × 1547 → 1009 × 1513

Same three files, re-run at a 97 KB target (99,328 bytes) in the same session. The 600 × 750 result sits 14% under the limit because the quality search steps in whole percent — 84% gave 100,825 bytes and the next step down, 83%, gave 85,669.

Note what the 97 KB column does not do: it does not buy a better picture. On the two files already at the 40% floor it bought fewer pixels (1140 × 1140 down to 1120 × 1120; 1031 × 1547 down to 1009 × 1513). That is the correct trade if a form is measuring your bytes, and the wrong one if it is not.

What to do, depending on what your form actually says

  1. Form names a pixel size and a byte ceiling. Crop to the pixel size first, then compress. Doing it in the other order wastes pixels: the compressor will scale a 4000 × 6000 file down to 1031 × 1547, and then you crop a small picture out of that. At the portal's own size the same 100 KB gave 84% quality at 600 × 750.
  2. Form names only a byte ceiling. Set the target to 97 KB if the number is written as 100 KB, and check the output byte count rather than the rounded label — 100 KB in the interface is 102,400 bytes.
  3. Form names a floor as well as a ceiling. Check the floor before compressing. The UK passport will not take a file under 50 KB; New Zealand will not take one under 250 KB, which rules out 100 KB entirely.
  4. Form accepts a wide pixel range. Use the bottom of the range. Canada's 715 × 1000 kept every pixel at 75% quality at 100 KB; its 2000 × 2800 maximum came back at 1039 × 1454.
  5. Upload is a scan, not a photo. Expect half the pixels. A 1200 × 1200 scan kept 761 × 761 at 100 KB against 1140 × 1140 for a photograph of the same size.

Questions this page gets asked

Is 100 KB enough for a passport photo?

At the pixel sizes passport forms actually specify, yes — 600 × 600 came back at 87% quality, 600 × 750 at 84%, 715 × 1000 at 75%, 900 × 1200 at 52%, all with their dimensions intact. The exception is a form with a floor: New Zealand requires at least 250 KB, so a 100 KB file fails regardless of how good it looks.

Can a 1200 × 1200 photo be compressed to 100 KB?

Not this one. It was returned at 1140 × 1140, 1,299,600 pixels, 102,384 bytes, at the 40% floor. A 1200 × 1200 square crop is 0.079 bytes per pixel at that quality, so 100 KB covers about 1.3 million of its pixels, not 1.44 million.

Why is my file 102 KB when I asked for 100 KB?

Because 100 KB here means 102,400 bytes. Every file measured on this page came out between 100,825 and 102,384 bytes at that target. If your form means 100,000 bytes, set 97 KB.

Does the target change the picture quality or the pixel count?

Quality first, pixels second. Between 600 × 600 and 900 × 1200 the dimensions never moved and quality fell from 87% to 52%. Past that point quality is pinned at 40% and the pixel count absorbs the rest, which is why 2000 × 2800 came back at 1039 × 1454.

All figures measured on 20 October 2026 with Chrome 155.0.8059.80 on Windows 11, using this site's compressor and one landscape photograph (Bachalpsee_reflection.jpg, Wikimedia Commons) at 4000 × 6000, centre-cropped to each pixel size, resized with Lanczos and saved at JPEG quality 92. The scanned page is a 4000 × 6000 render of 26 px text, cropped the same way. One photograph and one scan: sample points, not a distribution — a different picture will sit either side of 0.064 bytes per pixel. Portal rules were read on the government pages named in the table on the same day; they change, so check them again before you submit. The pixel-budget question at 20 KB is on the 20 KB page, at 50 KB on the 50 KB page, the ten-target ladder for one 24 MP file is on the ladder page, and whether a PNG can reach a tight byte target at all is on the PNG at 100 KB page.

Compress a JPG to 100 KB