Tap the image to enlarge
Rolex Datejust 31
Ref. 178240
See more premium optionsHide
Stepping up in Rolex's range
The Datejust name dates to 1945, when Rolex put a date window on a self-winding wristwatch and made it automatically advance at midnight — a first at the time. The 31mm midsize sits in a deliberate gap: larger than the classic ladies' proportions, smaller than the full 36mm, and for decades the preferred size for wearers who wanted the complete Datejust proposition without the weight and presence of the bigger case. The 178240 is the five-digit generation of that idea, built on the smooth domed bezel in plain Oystersteel rather than fluted precious metal, which keeps the whole thing unassertive in a way the flashier configurations do not. At 31mm with a lug-to-lug of 37mm it settles closely against the wrist, and the domed bezel gives the dial surround a quiet depth that a flat one would not. The Calibre 2235 inside holds COSC chronometer certification, built entirely in-house, and it is the movement Rolex used across this line before the 278240 took over with the updated 2236. A 48-hour reserve means a weekend off the wrist causes no problem on Monday morning. The Oyster bracelet's screwed links allow precise sizing without sending it anywhere — a straight-sided link removed or added at home with the right tool.
- Reference
- 178240
- Brand
- Rolex
- Collection
- Datejust
- Case size
- 31mm
- Case thickness
- 11mm
- Lug width
- 16mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Grey
- Crystal
- Sapphire
- Movement
- Automatic
- Calibre
- 2235
- Functions
- Date
- Water resistance
- 100m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Folding clasp
- Lume
- Luminous
- Retailer
- Goldsmiths
Additional specifications
- Lug-to-lug
- 37mm
- Power reserve
- 48 hours
Learn more about Rolex
Hans Wilsdorf founded Wilsdorf & Davis in London in 1905 with his brother-in-law Alfred Davis, importing Swiss movements and casing them in England. He registered the name Rolex in 1908 — short, pronounceable in any language, and easy to fit on a dial.
Wilsdorf's conviction was that the wristwatch, then regarded as a woman's ornament and hopelessly fragile, could be made accurate and durable. He proved the first half in 1910 by obtaining the first chronometer certification for a wristwatch, and the second in 1926 with the Oyster case, sealed by a screw-down crown and caseback. Mercedes Gleitze swam the Channel wearing one in 1927, and Wilsdorf bought the front page of the Daily Mail to say so — arguably the first modern watch marketing campaign.
The Perpetual rotor followed in 1931, giving automatic winding in a form the whole industry eventually copied. The company relocated to Geneva during the First World War to escape British wartime duties.
The professional models arrived in a compressed burst in the 1950s: Submariner, Explorer, GMT-Master, Milgauss, and later the Daytona. Each was built for a specific job — diving, exploration, aviation, laboratory work, racing — and each became a design template.
Wilsdorf left his shares to a private foundation on his death, so Rolex answers to no shareholders. It remains the largest producer of certified chronometers in Switzerland by a wide margin.
- 1905
- Hans Wilsdorf founds Wilsdorf & Davis in London.
- 1908
- The Rolex name is registered.
- 1926
- The Oyster case introduces genuine water resistance.
- 1931
- The Perpetual rotor brings modern automatic winding.
- 1953
- The Submariner and Explorer launch.
- 1963
- The Cosmograph Daytona arrives.
Also in 3 collections
This watch appears in Stainless Steel Watches (3,355), Watches Under 37mm (1,771) and Automatic Watches (1,699).
Manufacturer’s guarantee
What the specifications mean
A mechanical watch for everyday wear.
Strengths
- 100m water resistance covers swimming and watersports
- 31mm wears small and slips under any cuff
- Sapphire crystal, which resists scratching
- Luminous hands and markers for low light
- Sits in the lower half of Rolex's range as we list it
Rolex Datejust 31 alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | 178240 | STGK033 | 278573-3012 |
|---|---|---|---|
| Price | £7,350 | £5,900 | £7,940 |
| Case size | 31mm | 30mm | 30mm |
| Water resistance | 100m | 100m | 30m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Stainless steel bracelet | Stainless steel bracelet | Stainless steel bracelet |
| Power reserve | 48 hours | 50 hours | 42 hours |
| This watch |
|
|
Your new watch
Frequently asked questions, and things you should know about this watch
Can I swim with it?
Yes. At 100m it is rated for swimming and snorkelling, though not for diving.
Will the glass scratch?
Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.
Does it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
How long does it run for when it's not worn?
About 48 hours fully wound — enough to survive a night off the wrist, but not a full weekend.
What size strap does it take?
16mm. Any strap of that width will fit, and on most modern watches quick-release bars make the swap a two-minute job with no tools.
Will it fit my wrist?
Lug-to-lug is 37mm, which suits wrists from roughly 15cm (6 inches) upward.
Lug-to-lug decides fit more than case diameter does.
Is it a men's or women's watch?
Listed as unisex, and at this size it suits any wrist that takes the dimensions.
Cheapest place to buy
Goldsmiths at £7,350, against £7,450 at Goldsmiths. Two UK retailers stock this reference new.
Who are Goldsmiths?
Goldsmiths has been selling watches in Britain since 1778 and is part of the Watches of Switzerland Group, which is listed on the London Stock Exchange. They are an authorised dealer, so a watch comes with the manufacturer’s own warranty.
More Rolex watches like the Datejust 31
In stock, and close on style and price
