Apple credits the iPhone 18 Pro and Pro Max battery gains to bigger battery designs and more efficient silicon. One independent lab has now put numbers on them. Both phones outlasted last year's models in testing, but by less than an hour. For iPhone 17 Pro and 17 Pro Max owners, that makes battery life a thin reason on its own to upgrade. For anyone already committed to a new Pro, the battery question that matters is which size to buy.
Tom's Guide published its endurance results on Sept. 16. The lab set each display to 150 nits and ran continuous simulated web browsing over a cellular connection until the phone shut down. The iPhone 18 Pro averaged 16 hours 17 minutes; the iPhone 18 Pro Max averaged 18 hours 27 minutes. Under the same test, the iPhone 17 Pro averaged 15 hours 21 minutes and the iPhone 17 Pro Max 17 hours 54 minutes.
By Tom's Guide's math, that's a 56-minute gain (6.1%) for the Pro and a 33-minute gain (3.1%) for the Pro Max. Real improvements, but single digits, from one lab running one workload.
The size gap is bigger than the year gap
If you're buying a new Pro rather than holding onto an old one, the choice between the two sizes does more for your battery than the model year did. In the same test, the Pro Max ran 2 hours 10 minutes longer than the Pro, roughly 13% more endurance. That's more than twice the largest year-over-year gain Tom's Guide measured. The Pro Max starts at $1,299, $100 above the Pro's $1,199, and both have been on sale in the U.S. since Sept. 18.
Apple's own ratings, which come from a different test, put the gap between the sizes wider still — about 25%. The two sources disagree on how big the gap is. They agree on its direction: the Pro Max lasts longer.
What Apple rates, and why it doesn't line up
In its Sept. 9 announcement, Apple rated the U.S. eSIM-only iPhone 18 Pro for up to 36 hours of video playback and the Pro Max for up to 45 hours. It also puts the Pro Max at up to 30 hours of typical use under its own usage model. Dropping the physical SIM from U.S. models, Apple says, freed space worth two additional hours of video playback.
None of that lines up with Tom's Guide's results, and it isn't meant to. Video playback, Apple's typical-use model and continuous cellular browsing are different workloads run under different conditions. Apple also calls the eSIM-only Pro Max its largest battery-life increase ever without attaching a number to the claim on the announcement page. The 3.1% browsing result doesn't necessarily contradict it, because the two sources measure different things.
Fast charging needs the right gear
Apple says a drained iPhone 18 Pro can reach 50% in about 15 minutes. The fine print: that takes a 60W-capable adapter that supports Adjustable Voltage Supply and a compatible USB-C cable, both sold separately, and Apple ran those tests on preproduction hardware and software. Before counting on that speed from a charger you already own, check it against both requirements.
Your own battery life won't match a lab result either. Signal strength, screen brightness, which apps you run, camera use, gaming and background activity all move the number. What this testing shows is narrower: the 18 Pro models last somewhat longer than last year's, and the Pro Max held a clear lead over the Pro.