iPhone 18 and the foldable Duo are here, and Apple still charges ~$100-200 per storage tier. Sixty seconds of math before you pay for empty space.
The quick answer
256GB fits ~100,000 HEIC photos or 30+ hours of 1080p — enough for most, after ~20GB for iOS + apps. Take 512GB if you shoot 4K weekly, keep ProRAW, or go Duo (foldables collect more video, screenshots and app weight). 1TB is for ProRes videographers only. Whatever you buy, a cleanup pass frees the equivalent of a tier free — run your numbers in our photo storage calculator.
The math per size (usable ≈ advertised − 20GB iOS/apps)
| Size | Usable | HEIC photos | 4K60 video hours |
|---|---|---|---|
| 128GB | ~108GB | ~65,000 | ~4.5h |
| 256GB | ~236GB | ~140,000 | ~10h |
| 512GB | ~492GB | ~300,000 | ~20h |
| 1TB | ~1,000GB | ~600,000 | ~40h |
What the table gives you: photo counts are never the constraint — video is. One 4K60 hour eats what 25,000 photos use. What it does not give you: your apps’ share. Games, offline maps and Duo multitasking panels take their cut first — see what’s taking up space.
Duo-specific advice
The foldable’s big screen changes habits: more video watched (more offline downloads), more screenshots (split-screen moments), bigger apps. None of it is huge alone; together it’s a tier. If you’re switching from a slab iPhone, assume +20-30GB of lifestyle weight — or clean before migrating so the Duo starts empty (transfer guide).
The bottom line
Buy 256GB (512GB for Duo power users), shoot HEIC (HEIC vs JPEG), clean twice a year. The $200 saved buys a very nice SSD (move photos to SSD).