If you are choosing between the iPhone 18 Pro and the iPhone 18 Pro Max because you want the one that holds its speed longest in a long game or a long take, Apple has published nothing to help you. It describes one cooling system, a next-generation vapor chamber attached directly to the chip with about three times the cooling performance of the previous design, and it describes it identically for both sizes.
That is a real gap rather than a pedantic one. The Pro Max is a larger body at the same 8.75 mm thickness, 163.4 x 78.0 mm against 150.0 x 71.9 mm and 249 g against 211 g, so there is more of it to move heat into. Apple has not said whether that changes anything, and the only performance-adjacent numbers it splits by size are the battery ratings.
Key facts: what Apple publishes, and whether it varies by size
| Item | What Apple publishes | Varies by size? |
|---|---|---|
| Cooling hardware | Next-generation vapor chamber attached directly to the chip | No |
| Cooling claim | About three times the cooling performance of the prior design | No |
| Chip | A20 Pro, 6-core CPU, 7-core GPU, dual 16-core Neural Engine | No |
| GPU claim | Up to 40 percent faster than A19 Pro | No |
| Memory bandwidth | 50 percent more than A19 Pro | No |
| Sustained performance figure | Not published for either model | Not published |
| Thermal throttling behavior | Not published for either model | Not published |
| Body and weight | 150.0 x 71.9 x 8.75 mm, 211 g; 163.4 x 78.0 x 8.75 mm, 249 g | Yes |
| Battery ratings | 36 hours video and 24 typical; 45 hours video and 30 typical | Yes |
| Charging claims | 50 percent in around 15 minutes with a 60W adapter | No |
One cooling claim, two different volumes
Apple’s comparison for the vapor chamber is against the previous design, not against the other size, and it is a single figure quoted for the generation. Nothing in the announcement or the tech specs distinguishes the thermal design of the 6.3-inch phone from the 6.9-inch one.
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Both phones also list the same chip down to the core counts, the same aluminum unibody, the same Ceramic Shield 2 front and Ceramic Shield back, and the same IP68 rating to 6 meters for 30 minutes. Our A20 Pro explainer goes through every performance claim Apple attached to the chip, none of which is stated per model.
The only split Apple does publish
| Line | iPhone 18 Pro | iPhone 18 Pro Max |
|---|---|---|
| Typical use | Up to 24 hours | Up to 30 hours |
| Video playback | Up to 36 hours | Up to 45 hours |
| Streamed video | Up to 33 hours | Up to 40 hours |
| Five-minute charge | Not published | About seven hours of video playback |
| Weight | 211 g | 249 g |
| US price, 256GB | $1,199 | $1,299 |
Longer battery ratings are not a thermal claim. They describe playback, which is a light and steady load, not the sustained load that makes a phone warm. Apple documents update warmth and post-update battery drain in its own support articles, and publishes nothing equivalent about heat under heavy use on either size. Our battery and charging explainer sets out what each rating measures.
Where it would show up if it mattered
- Long recordings. Both models list 4K Dolby Vision at up to 120 fps and ProRes at 4K120 with external recording, and Apple rates no recording time for either.
- Games with hardware-accelerated ray tracing, where Apple’s only figure is the 40 percent GPU claim against last year’s chip.
- Fast charging, where both are rated for 50 percent in around 15 minutes with a 60W adapter, an adapter Apple has not priced.
- Wireless charging, where both stop at 25W over MagSafe and 25W over Qi2.
- On-device Apple Intelligence work, where Apple’s claims are stated for the chip rather than for either phone.
Until the phones are in hand and tested, the honest answer to the thermal version of the size question is that Apple has not answered it. Our Pro against Pro Max comparison and the launch-day specification rundown set out the differences it did publish.
What Apple has not said
- Any sustained-performance figure for the iPhone 18 Pro or the iPhone 18 Pro Max, together or separately.
- Whether the vapor chamber is the same size in both phones, or scaled with the body.
- Any operating temperature range, throttling threshold or thermal test condition for either model.
- How long either phone can record 4K at 120 fps or ProRes before anything changes.
- Any benchmark. Every A20 Pro claim is relative to the A19 Pro, with no test conditions attached.
Pre-orders open at 5 a.m. PT on Saturday, September 12, which is 12:00 UTC, and both sizes reach stores on Friday, September 18. Anyone buying on thermal grounds is buying on inference, because the only published difference between the two bodies is 38 g, 6.1 mm of width and 13.4 mm of height.
