Jordan 4 sizing threads are a battlefield. One comment says “TTS, who told you to size up?”, the next says “half up or your pinky toes are done”. Owners compare notes on this in Jordan 1 Low sizing. Who’s right? 
Related threads: Jordan 4 on feet, the thread on Yeezy 350 V2 reps and the thread on Dunk Low sizing.
Both, for different feet!
Shape: the J4 has a fairly firm toe box and a structured upper. It doesn’t give much.
Common advice: TTS for normal or narrow feet, half up for wide feet.
Batch footnote: several people report specific J4 batches, GX among them, feeling snug in the toe box at their usual size. Others say the same batch felt roomy. Feet differ.
Important: a lot of people mix up length and width. If your toes don’t hit the front but it pinches at the sides, that’s a width problem. Half a size up helps a bit then, but not just because of the length.
Ok but if it’s tight, can’t you just wear it in? Like boss fight, eventually you win.
Up to a point. Leather stretches a little in width, but the J4 has a lot of reinforced parts. One thread mentioned a cobbler stretching the shoe on a last. It helped “a bit”. I wouldn’t count on it.
Another source of confusion: sizes. Several threads point out that many factories label in EU sizes, and the EU-to-US conversion isn’t identical across brands. Always check which number is the real one on the size tag.
And insole measurements? Someone in a thread said comparing them to your retail pair was “meaningless”.
Not meaningless, just incomplete. Insole length says nothing about toe box height or width, which is exactly where J4s pinch. Use it as one data point.
Summed up so you can decide straight away:
1. Measure your feet: length and width in cm, in the evening, both feet.
2. Starting point:
| Foot | Advice from the threads |
|---|---|
| narrow/normal | TTS |
| wide | ½ up |
| very wide | ½ up, and honestly check whether the J4 suits you at all |
3. Factor in the batch: read the latest user reports on that specific batch. Some are described as tight in the toe area.
4. Check the size tag: read the EU size on the tag, not just the US size in the listing text.
5. QC photos: ask for a top-down view of both shoes and a side view to see toe box height and width.
[[PHOTO: top-down view of a pair of Jordan 4s showing toe box width at the widest point]]
6. Don’t count on stretching. Leather gives a little, the reinforced parts barely at all.
In short: normal feet TTS, wide feet ½ up, and always read the batch reports.
Clean answer. Value score 5/5, marking it. Boss fight avoided. 
And a tip for comparing: the J1 is a good reference for length, but the J4 is narrower up front. If your J1 size is already snug, go half up on J4s.