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MobileIQ

Head to head

Apple Apple Watch Series 12 46mmvsApple Apple Watch SE 3 40mm

Released
2026-09-18Apple UK Newsroom — Apple Watch Series 12, retrieved 2026-09-13
Price
£419Apple UK store — Series 12 46mm aluminium GPS, retrieved 2026-09-22
Security updates until
Not published by the makerApple UK — watchOS 27 compatible models, retrieved 2026-09-22
Released
2025-09-19Apple Newsroom — Apple Watch SE 3, retrieved 2026-09-13
Price
£219Apple UK store, retrieved 2026-09-13
Security updates until
Not published by the makerApple UK — watchOS 27 compatible models, retrieved 2026-09-22

1 win for Apple Watch Series 12 46mm1 win for Apple Watch SE 3 40mm1 gap borderline1 difference you won’t notice£200 apart at RRP

Verdict: Apple Watch Series 12 46mm ahead on 1 row, Apple Watch SE 3 40mm on 1 row

On the makers’ published figures, the Apple Watch Series 12 46mm wins on peak brightness (2,000 nits against 1,000 nits); the Apple Watch SE 3 40mm wins on weight (case only) (26.3 g against 39.5 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 12 46mm. The difference in battery life (maker's claim) is below the threshold you would notice. The other 25 rows have no threshold or no direction to judge by, so nobody wins them.

True to scale

Apple Watch Series 12 46mm · 46 × 40 mmApple Watch SE 3 40mm · 40 × 34 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 Series 12 46mmApple Watch SE 3 40mm
DimensionsDiffers, but not ranked.
46 x 40 x 9.7 mmOfficial
40 x 34 x 10.7 mmOfficial
Case size
46mmOfficial
40mmOfficial
Case shapeSame.
rectangularOfficial
rectangularOfficial
Weight (case only)
39.5gOfficial
26.3gOfficialwins this row

Apple Watch SE 3 40mm is ahead here, by a gap you’d notice.

Case materialSame.
AluminiumOfficial
AluminiumOfficial
Water ratingDiffers, but not ranked.
Water resistance 50m (swimproof) under ISO standard 22810:2010Official
Water resistance 50m (swimproof)Official

Display

SpecificationApple Watch Series 12 46mmApple Watch SE 3 40mm
Display typeDiffers, but not ranked.
Always-On Retina display with wide-angle OLEDs and LTPO3Official
Always-On Retina display with OLED and LTPOOfficial
Display areaDiffers, but not ranked.
1196mm²Official
759mm²Official
ResolutionDiffers, but not ranked.
416 x 496Official
324 x 394Official
Peak brightness
2000nitsOfficialwins this row
1000nitsOfficial

Apple Watch Series 12 46mm is ahead here, by a gap you’d notice.

Always-on displaySame.
YesOfficial
YesOfficial

Platform

SpecificationApple Watch Series 12 46mmApple Watch SE 3 40mm
Operating systemDiffers, but not ranked.
watchOS 27Official
watchOS 26Official
ChipDiffers, but not ranked.
S11 SiPOfficial
S10 SiPOfficial
StorageSame.
64GBOfficial
64GBOfficial

Battery

SpecificationApple Watch Series 12 46mmApple Watch SE 3 40mm
Battery life (maker's claim)
24hOfficial
18hOfficial

You won’t notice this difference.

Charge to 80%
30minOfficial
45minOfficial

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 Series 12 46mmApple Watch SE 3 40mm
SensorsDiffers, but not ranked.
Health Sensing System (third-generation electrical heart sensor, always-on optical heart sensor, blood oxygen sensor, temperature sensor), compass, always-on altimeter, high-g accelerometer, high dynamic range gyroscope, ambient light sensor, depth gauge to 6 metres, water temperature sensorOfficial
Second-generation optical heart sensor, temperature sensor, compass, always-on altimeter, high-g accelerometer, high dynamic range gyroscope, ambient light sensorOfficial
ECGDiffers, but not ranked.
YesOfficial
NoOfficial
Blood oxygenDiffers, but not ranked.
YesOfficial
NoOfficial
Skin temperatureSame.
YesOfficial
YesOfficial
GPSDiffers, but not ranked.
Precision L1 GPS (GPS, GLONASS, Galileo, QZSS and BeiDou)Official
L1 GPS (GLONASS, Galileo, QZSS and BeiDou)Official

Connectivity

SpecificationApple Watch Series 12 46mmApple Watch SE 3 40mm
Cellular modelSame.
YesOfficial
YesOfficial
UK networks with eSIMDiffers, but not ranked.
EE, Vodafone, 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 Series 12 46mmApple Watch SE 3 40mm
Works withSame.
iPhone 11 or later, including iPhone SE (2nd generation or later), with iOS 27 or laterOfficial
iPhone 11 or later, including iPhone SE (2nd generation or later), with iOS 27 or laterOfficial
CompatibilitySame.
iPhone onlyOfficial
iPhone onlyOfficial
6 attributes neither watch has a sourced figure for

Strap width · Display size · RAM · Battery capacity · 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.