Apple Watch Series 9 vs Apple Watch Ultra 4

Series 9 has been around since 12 September 2023, when Apple announced it, and went on sale on 22 September running watchOS 10. Three years on, it’s the oldest everyday Series that gets watchOS 27, and Apple has kept adding health features to it through software. What no update can give it is any of Ultra 4’s hardware.

The spec gap

Spec	Apple Watch Series 9	Apple Watch Ultra 4
Announced	12 September 2023	9 September 2026
Sizes	41mm or 45mm	49mm only
Thickness	10.7mm	12mm
Case	Aluminum or stainless steel	Grade 5 titanium
Display	Always-On LTPO, 2,000 nits	Always-On LTPO3, 3,000 nits
Chip and storage	S9; 64GB	S11; 64GB
Heart sensors	Third-generation optical	Health Sensing System
Normal use	Up to 18 hours	Up to 50 hours
Low Power Mode	Up to 36 hours	Up to 84 hours
Charge to 80%	About 45 minutes	About 45 minutes
GPS	L1	Dual-frequency
Cellular	LTE and UMTS	5G RedCap and LTE
Depth gauge	No	Yes, to 40m
Satellite	No	SOS, Messages, Find My
watchOS 27	Yes	Ships with it
US launch price	$399	$799

Screen, chip and case

Series 9 runs the S9, a 64-bit dual-core chip with a 4-core Neural Engine that handles double tap and on-device Siri, and it has the same 64GB of storage as Ultra 4. Its Always-On LTPO screen peaks at 2,000 nits and dims to 1 nit at 326 ppi; it isn’t the wide-angle LTPO3 panel that arrived with Series 10. Aluminum models use Ion-X glass and stainless steel models sapphire. There’s no titanium Series 9: Series 10 was the one that swapped steel for titanium.

The case measures 41 × 35 × 10.7mm or 45 × 38 × 10.7mm. The 41mm aluminum GPS model weighs 31.9 grams and the 45mm 38.7 grams, and stainless steel weighs 42.3 or 51.5 grams. The smaller size fits wrists from 130 to 200mm, the larger from 140 to 245mm. Aluminum came in pink, midnight, starlight, silver and (PRODUCT)RED, and stainless steel in gold, silver and graphite; pink is a color the Ultra has never offered.

Ultra 4 comes in a single 49mm titanium size, 12mm thick and 63 grams, with a 422 × 514 screen that peaks at 3,000 nits under sapphire on every model.

Battery: 18 hours against 50

Series 9’s brighter 2,000-nit screen didn’t come with more battery life. It’s rated for up to 18 hours, or 36 in Low Power Mode, and charges to about 80 percent in about 45 minutes. Ultra 4 takes the same 45 minutes to reach 80 percent, then keeps going: up to 50 hours of normal use and 84 in Low Power Mode, plus its GPS workout modes. If your Series 9 already gets you to bedtime, battery alone won’t justify the Ultra.

Health features that came in software

Series 9 has picked up health features through updates: hypertension notifications, sleep apnea notifications, a Sleep score and the Vitals app, which follows your heart rate, respiratory rate, wrist temperature and sleep duration overnight. Sleep apnea notifications are for people 18 and older and point to possible signs, not a diagnosis. ECG is the single-lead app for people 22 and older, Blood Oxygen is a wellness feature, and the temperature sensor tracks your wrist overnight; it isn’t a medical thermometer.

The Health Sensing System is where software stops. Series 9 keeps its third-generation optical heart sensor, so it doesn’t get five-second background heart rate, the readiness score or Audio Intelligence; those need S11, on Series 12 and Ultra 4.

Outdoors, Ultra 4 pulls away

Series 9 is water resistant to 50 meters for shallow swimming, with IP6X dust resistance, no depth gauge and no MIL-STD testing. Its GPS is L1, working with GPS, GNSS, Galileo and BeiDou, and its cellular models use LTE and UMTS rather than 5G. It also has Wi-Fi 4, Bluetooth 5.3 and a second-generation ultra-wideband chip, and it’s rated for 0 to 35 degrees Celsius and altitudes up to 3,000 meters. Ultra 4 adds dual-frequency GPS, 5G RedCap, a 40-meter dive rating and satellite messaging.

Workouts on Series 9 come in running, hiking, cycling and swimming sections plus a list of other workouts, without the extra metrics Apple lists for Ultra 4, such as running power, Race Route, Functional Threshold Power and SWOLF. For the outdoors, Apple’s Series 9 specs stop at the compass, the always-on altimeter and those workout sections; offline maps and the 63-park hike list show up in the specs for later Series and Ultra models. Series 9 has no Action Button, no siren and no Night Mode for the Wayfinder face.

Pairing, bands and price

Series 9 pairs with an iPhone Xs or later on iOS 17 or later, though a current watchOS release can need a newer iPhone; Ultra 4 needs an iPhone 11 or later on iOS 27. Both have Apple Pay and GymKit, and both offer accessibility features such as VoiceOver, Zoom and AssistiveTouch. Apple Watch For Your Kids works on cellular Series 9 models, with some features missing on a managed watch.

The Series 9 box has the watch, one band and a magnetic fast charger to USB-C. It uses the standard band fitting, so an Ultra Alpine Loop won’t fit.

Series 9 launched at $399 and Ultra 4 at $799. If you want the Health Sensing System in an everyday size, buy Series 12 from $399 rather than a used Series 9. Check apple.com before you buy, and don’t pay near-Ultra money for a Series 9: that’s an adventure price for a watch without the adventure hardware.