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MobileIQ

Head to head

Apple Apple Watch Ultra 3 49mmvsApple Apple Watch Series 10 42mm

Released
2025-09-19Apple UK Newsroom — Apple Watch Ultra 3, retrieved 2026-09-13
Security updates until
Not published by the makerApple UK — watchOS 27 compatible models, retrieved 2026-09-22
Released
2024-09-20endoflife.date, retrieved 2026-09-13
Security updates until
Not published by the makerApple UK — watchOS 27 compatible models, retrieved 2026-09-22

2 wins for Apple Watch Ultra 3 49mm1 win for Apple Watch Series 10 42mm1 gap borderline0 differences you won’t notice

Verdict: Apple Watch Ultra 3 49mm ahead on 2 rows, Apple Watch Series 10 42mm on 1 row

On the makers’ published figures, the Apple Watch Ultra 3 49mm wins on peak brightness (3,000 nits against 2,000 nits) and battery life (maker's claim) (42 h against 18 h); the Apple Watch Series 10 42mm wins on weight (case only) (30 g against 61.6 g). One gap is borderline, a difference most people would not notice: charge to 80% (30 min against 45 min) for the Apple Watch Series 10 42mm. The other 26 rows have no threshold or no direction to judge by, so nobody wins them.

True to scale

Apple Watch Ultra 3 49mm · 49 × 44 mmApple Watch Series 10 42mm · 42 × 36 mm

Case outlines from each maker’s published dimensions, drawn to scale. Corner rounding is our drawing convention, not a measurement.

Specifications

A win is marked only where the figures can be ranked and the gap is one you could notice on the wrist. A row the site has no threshold for says whether the two differ, and that it is not ranking them. = marks the same figure on both, ≠ not ranked a difference with no ranking. Every figure carries its source.

Body

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
DimensionsDiffers, but not ranked.
49 x 44 x 12 mmOfficial
42 x 36 x 9.7 mmOfficial
Case size
49mmOfficial
42mmOfficial
Case shapeSame.
rectangularOfficial
rectangularOfficial
Weight (case only)
61.6gOfficial
30gOfficialwins this row

Apple Watch Series 10 42mm is ahead here, by a gap you’d notice.

Case materialDiffers, but not ranked.
TitaniumOfficial
AluminiumOfficial
Water ratingDiffers, but not ranked.
Water resistance 100m (swim, snorkel, scuba, high-speed water sports) under ISO standard 22810:2010; EN13319 recreational scuba diving to 40mOfficial
Water resistance 50m (swimproof)Official

Display

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
Display typeDiffers, but not ranked.
Always-On Retina display with wide-angle OLEDs and LTPO3Official
Always-On Retina LTPO3 displayOfficial
Display areaDiffers, but not ranked.
1245mm²Official
989mm²Official
ResolutionDiffers, but not ranked.
422 x 514Official
374 x 446Official
Peak brightness
3000nitsOfficialwins this row
2000nitsOfficial

Apple Watch Ultra 3 49mm is ahead here, by a gap you’d notice.

Always-on displaySame.
YesOfficial
YesOfficial

Platform

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
Operating systemDiffers, but not ranked.
watchOS 26Official
watchOSOfficial
ChipSame.
S10 SiPOfficial
S10 SiPOfficial
StorageSame.
64GBOfficial
64GBOfficial

Battery

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
Battery life (maker's claim)
42hOfficialwins this row
18hOfficial

Apple Watch Ultra 3 49mm is ahead here, by a gap you’d notice.

Battery capacity
599mAh3rd party
No verified data
Charge to 80%
45minOfficial
30minOfficial

Marginal — most people won’t notice.

ChargingSame.
Fast-charge capable, Apple Watch Magnetic Fast Charger to USB-C CableOfficial
Fast-charge capable, Apple Watch Magnetic Fast Charger to USB-C CableOfficial

Health

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
SensorsDiffers, but not ranked.
Electrical heart sensor, third-generation optical heart sensor, blood oxygen sensor, temperature sensor, depth gauge, water temperature sensor, compass, always-on altimeter, high-g accelerometer, high dynamic range gyroscope, ambient light sensorOfficial
Electrical heart sensor, third-generation optical heart sensor, temperature sensor, compass, always-on altimeter, high-g accelerometer, high dynamic range gyroscope, ambient light sensor, depth gauge, water temperature sensorOfficial
ECGSame.
YesOfficial
YesOfficial
Blood oxygen
YesOfficial
No verified data
Skin temperatureSame.
YesOfficial
YesOfficial
GPSDiffers, but not ranked.
L1 and L5 precision dual-frequency GPS (GPS, GLONASS, Galileo, QZSS and BeiDou)Official
L1 GPS, GNSS, Galileo and BeiDouOfficial

Connectivity

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
Cellular modelSame.
YesOfficial
YesOfficial
UK networks with eSIMSame.
EE, Vodafone, O2, Three3rd party
EE, Vodafone, O2, Three3rd party
Wi-FiSame.
Wi-Fi 4 (802.11n)Official
Wi-Fi 4 (802.11n)Official
BluetoothSame.
5.3Official
5.3Official
NFC paymentsSame.
YesOfficial
YesOfficial

Compatibility

SpecificationApple Watch Ultra 3 49mmApple Watch Series 10 42mm
Works withDiffers, but not ranked.
iPhone 11 or later, including iPhone SE (2nd generation or later), with iOS 26 or laterOfficial
iPhone Xs or later with iOS 18 or later and iPhone SE (2nd generation or later)Official
CompatibilitySame.
iPhone onlyOfficial
iPhone onlyOfficial
5 attributes neither watch has a sourced figure for

Strap width · Display size · RAM · Blood pressure · Cellular model price. Rows appear as sources are cited — a gap in our data, not a statement about either watch.

The pairs a buyer of either watch would also weigh. Any two watches in the catalogue can be compared from the chooser.