iPhone 18 Pro Max lasted 18 hours 27 minutes in an independent battery test

iPhone 18 Pro Max ran for 18 hours and 27 minutes of continuous web browsing over cellular before shutting down in Tom’s Guide’s standard battery test, published September 16, and the smaller iPhone 18 Pro lasted 16 hours and 17 minutes. Both beat last year’s models, the Pro Max by 33 minutes and the Pro by 56, smaller gains than Tom’s Guide expected given Apple’s emphasis on the A20 Pro’s efficiency.

Apple’s own numbers are video playback ratings, which measure something different; we covered those when Apple made the Pro Max the only iPhone rated at 45 hours.

How the test works

The method is simple and repeatable. Tom’s Guide describes it as “setting displays to 150 nits and running an automated script that simulates web browsing over a cellular connection until the device shuts off.” Every phone gets the same brightness, the same script and the same kind of connection, which is what makes the results comparable across years and brands.

It is not a picture of your day. Real use mixes the camera, games, navigation, higher brightness outdoors and long stretches of standby. What the test does give you is a fair ranking of phones under one steady load.

The iPhone results, year by year

Tom’s Guide published results for the last three generations of Pro iPhones, all from the same test:

The smaller phone made the bigger jump. The 18 Pro’s 56-minute gain over the 17 Pro works out to 6.1 percent, while the Pro Max’s 33 minutes over the 17 Pro Max is 3.1 percent. Tom’s Guide called the numbers “surprising given the heavy emphasis placed on the A20 Pro’s power efficiency,” and summed up the pair as “an improvement, but could be better.”

Against Android flagships

The same test puts the Pro Max comfortably ahead of Samsung and Google, and a long way behind OnePlus:

The Pro Max beats the Galaxy S26 Ultra by 1 hour 47 minutes and the Pixel 11 Pro XL by nearly four hours. The iPhone 18 Pro trails the Galaxy S26 Ultra by 23 minutes despite being the much smaller phone.

The OnePlus 15 outlasted the Pro Max by more than six and a half hours. Tom’s Guide credits its 7,300 mAh silicon-carbon battery and argues that Apple’s “reliance on conventional lithium-ion batteries has clearly reached its limits.” Apple’s spec sheet does list a “built-in rechargeable lithium-ion battery” for both iPhone 18 Pro models. Whether silicon-carbon is the fix is Tom’s Guide’s opinion, not something the test measured.

How this squares with Apple’s figures

Apple rates iPhone 18 Pro Max for up to 45 hours of video playback, 40 hours of streamed video and up to 30 hours of what it calls typical use. For iPhone 18 Pro the figures are 36, 33 and 24 hours. None of those is a web-browsing test, so they cannot be checked against the 18-hour result directly. Where both sources agree is the ranking: the Pro Max is the longer-lasting phone by a clear margin, and in this test the gap between the two models is just over two hours.

If you are judging your own phone in its first week, note that iPhone 18 Pro Adaptive Power does nothing for the first 7 days. If you care more about long-term battery health than maximum runtime, you can also set a charge limit and still charge to full when you need it.