How Large a HEIC Can This Converter Take?

Short answer: I did not find one. I ran six HEIC files through the live converter at the default 85% quality, from a 4,032×3,024 file of 11,084,868 bytes up to a 12,000×9,000 file of 97,045,798 bytes — 108 megapixels — and every single one converted, each keeping its full resolution. The page itself contains no file-size or dimension check that I could find.

What I measured on this site: what you pay for a big file is waiting and memory, not refusal. The 12 MP file took 6,007 ms with the browser’s JavaScript heap peaking at 66.2 MiB; the 108 MP file took 75,996 ms and peaked at 513.7 MiB. Nothing errored, nothing was rejected, and nothing was resized.

Measured: six files, 12 MP to 108 MP

Each file was opened in a fresh page, converted at 85%, and its heap sampled while it worked:

Pixels	HEIC in	JPG out	Convert time	Wall clock	Peak heap	Result
4,032×3,024 (12.2 MP)	11,084,868 B	3,177,680 B	6,007 ms	6.1 s	66.2 MiB	Converted
6,000×4,500 (27.0 MP)	24,470,938 B	7,013,308 B	17,806 ms	18.0 s	135.5 MiB	Converted
7,680×4,320 (33.2 MP)	29,970,185 B	8,596,411 B	19,710 ms	19.9 s	166.4 MiB	Converted
8,000×6,000 (48.0 MP)	43,253,153 B	12,426,020 B	24,248 ms	24.4 s	233.6 MiB	Converted
10,000×7,500 (75.0 MP)	67,472,235 B	19,393,103 B	48,090 ms	48.3 s	359.6 MiB	Converted
12,000×9,000 (108.0 MP)	97,045,798 B	27,888,851 B	75,996 ms	76.1 s	513.7 MiB	Converted

Every output kept the exact pixel dimensions of its input — nothing was scaled down. And because I built all six from the same synthetic picture at different sizes, each JPG came out at 0.29× the size of its HEIC. That ratio is a property of that one picture, not a rule: real photographs vary, which is what the file-size measurements are about.

How the cost scales

Going from 12.2 MP to 108 MP is 8.9× the pixels. It cost 12.7× the time (6,007 ms to 75,996 ms) and about 7.8× the peak heap (66.2 MiB to 513.7 MiB). So the waiting grows a little faster than the picture does, and the memory grows roughly with it. There is no point where the page steps in and says no — it just gets slower and hungrier.

That peak of half a gigabyte is the part worth thinking about on a phone. I measured it on a desktop machine; I did not run these files on a phone, so I will not tell you what a phone does with them. What I can say is that the heap number is real, it is large, and it is the kind of number that decides whether a mobile browser survives.

What the page does and does not check

No size or dimension guard. I read the live page looking for one — a byte ceiling, a pixel ceiling, a “too large” message — and found none. The only place the word limit appears is marketing copy about there being no batch limit.
The file filter is a type filter, not a size filter: .heic,.heif,image/heic,image/heif.
One file at a time. The input is single-select, so a folder of large files is one round trip each — and at 76 seconds for the biggest file here, that adds up fast.
The decoder is fetched once per page load, not per file, so the wait is pure decoding. That first-load size is measured in the Android, Chromebook and Linux runs.

What to do if a huge file seems stuck

Wait before you give up. The largest file I ran took 76.1 seconds and was still healthy at the end. Nothing in the page told me it was going to fail at any point.
Watch the machine, not the page. If the browser is using hundreds of megabytes and the tab is busy, it is decoding, not hanging.
Consider a lower quality setting if you just need something shareable — the quality choice changes the output size, measured at three settings in the macOS comparison.

Questions

Is there a maximum file size?

I did not find one. The largest file I converted today was 97,045,798 bytes, and it went through normally.

Does it shrink the image to fit?

No. Every output matched its input exactly: 12,000×9,000 in, 12,000×9,000 out. There is no resize control on the page.

How long does a normal iPhone photo take?

A 12 MP photo of 1,267,632 bytes took 3,175–6,527 ms across eight runs in today’s other measurements. The files in the table above are far bigger than a normal photo — that is the point of them.

Will a huge file crash my phone?

Not measured. The peak heap on this desktop was 513.7 MiB for the 108 MP file; I have no phone number to compare it with, and I am not going to guess one.

Can I convert several large files at once?

No — the input takes one file at a time. The measured cost of doing many in a row is in the 200-file run, though those were ordinary 12 MP photos rather than these monsters.

What I could not measure

Anything past 108 MP, or past a file of 97,045,798 bytes. That is where I stopped, not where the converter stopped.
What happens when memory actually runs out. Nothing failed today, so I never saw the out-of-memory behaviour, and I will not describe it.
Phones, tablets and other browsers. All six runs were Chrome on one Windows desktop.
Real photographs at these sizes. These files were synthetic — the same picture rendered larger — so their 0.29× size ratio is not a general rule.

Got a file an online tool refused for being too big? Open the converter — there is no size box to hit, and nothing is uploaded.

First published: 27 September 2026

How large a HEIC can this converter take?