If you were a watch designer or movement engineer in the mid-1950s, you were likely sorted into one of three camps in seeking to summit your “Everest.” You were trying to create reliable high-beat movements with a 5 Hz frequency; or you were working diligently to invent the automatic chronograph; or you were attempting to go thinner than anyone ever had before.

Blancpain had just practically defined the new category of diver’s watches with the Fifty Fathoms, which followed Rolex’s accomplishments in creating the waterproof watch – all born of Cartier’s development of the purpose-built men’s wristwatch, the Santos-Dumont.

Heck, even the automatic wristwatch had pretty much been perfected within the last few decades, so the remaining goals were narrowing fast.

Utility and precision were the main dividing lines, and for some going as thin as possible showed the biggest challenges. In the age of “the future,” post-war productivity and ideas about what humanity could become now that global war was a thing of the past (oops) became the driving force for many innovations.

For those watchmakers intent on racing headlong into the future, watch movements that were paper thin and disappeared on the wrist felt like the right move.

Piaget was the undeniable champion in this field with the release of Caliber 9P in 1957 – the thinnest manually wound movement, only 2 mm in height – and the Caliber 12P in 1960, the thinnest automatic movement, only 2.3 mm in height.

Within the following decade the first quartz watches were developed, and thinness became a standard of that new technology. So it would be another few decades before watchmakers would seriously push the boundaries of thinness in mechanical watches.

We are now living in the modern race to the thinnest, and as records are set we have a bumper crop of incredibly thin watches that prove this competition may not be over yet. To celebrate the awesomazingness of these watches, I’ve compiled a list of the 10 thinnest mechanical watches, including a pair of historical pieces that provide context (and solid competition) for what brands are producing today.

Also please note, this list is based on total case thickness, not movement thickness, in case you know of a movement that comes in under these numbers. There are indeed many ultra-thin movements, but when cased up fall outside of this narrow range.

10. Historical Piaget 12103 Automatic 12P (1960): 5.00 mm

Starting with a historical piece coming in at a nice and round 5 mm height we have the original Piaget 12103 Automatic 12P, the first iteration of the 12P movement, the thinnest automatic movement in the world for quite a long time. The original watch comprised a very thin gold case housing Caliber 12P, which measured in at 2.30 mm.

The Piaget 12103 Automatic 12P pretty much set the standard for ultra-thin automatic watches and remained unchallenged by a production movement until this last decade when the race began anew.

For a watch and movement debuting exactly 60 years ago, the fact that it makes the top ten thinnest watches list in 2020 means it is one of the most ahead-of-its-time pieces of the twentieth century.

Quick Facts Piaget 12103 Automatic 12P
Case: yellow or white gold, 32 x 5 mm
Movement: automatic Caliber 12P, 2.3 mm in height, 19,800 vph frequency, 37-hour power reserve, 19 jewels
Functions: hours, minutes

9. Bulgari Octo Finissimo Tourbillon (2014): 5.00 mm

Tied with the original Piaget 12P in overall case thickness but smashing the movement thickness with a manually wound tourbillon caliber, the Bulgari Octo Finissimo Tourbillon first released in a platinum case comes in at a very thin 5 mm in height.

But the real point of amazement was the 1.95 mm tourbillon movement, a stunning accomplishment that most would have guessed to be impossible.

It was also the first major punch from Bulgari on the Octo Finissimo front, the brand grabbing record after record with the line over the coming years. The Octo Finissimo Tourbillon still stands as one of the thinnest tourbillon movements ever made and shows that Bulgari is not messing around.

Quick Facts Bulgari Octo Finissimo Tourbillon
Case: 40 x 5 mm, platinum
Movement: ultra-thin manually wound Finissimo Tourbillon Caliber with 60-minute flying tourbillon, 1.95 mm height, 32.6 mm diameter, 21,600 vph/3 Hz frequency, 55-hour power reserve, variable inertia balance
Functions: hours, minutes
Price: CHF 130,000

8. Piaget Altiplano Ultimate 910P (2017): 4.3 mm

Our next entry makes a big jump from the now-“hefty” 5 mm cases down to a trimmer 4.3 mm with the Piaget Altiplano Ultimate 910P. Coming within a year of the sensational Bulgari Octo Finissimo Automatic, the Piaget 910P stole back the crown for the thinnest automatic watch in the world (for a while).

Interestingly, though, it didn’t beat the Bulgari for movement thickness as its movement is integrated with the case. So while the movement thickness is technically thicker, this construction allowed for the dramatic reduction in case height.

Since you can’t wear a movement on its own, this shift in method boosted Piaget into a commanding lead. It wasn’t the first watch to try this construction technique (that was Audemars Piguet in 1986), but it used it utterly successfully, amping up the modern race to the thinnest watch possible.

Quick Facts Piaget Altiplano Ultimate 910P
Case: 41 x 4.3 mm, pink gold or white gold
Movement: automatic Caliber 910P, 50-hour power reserve, 21,600 vph/3 Hz frequency, 22-karat gold peripheral rotor
Functions: hours, minutes
Price: $26,000 (pink gold), $27,100 (white gold)

7. Vacheron Constantin Historiques Ultra-Fine 1955 (2010): 4.13 mm

At number seven things change up from the typical Piaget/Bulgari battle to find an awesomely thin piece from Vacheron Constantin. In the Genevan brand’s only appearance on this list, Vacheron Constantin makes a bold yet refined statement with the Historiques Ultra-Fine 1955, a modern interpretation of a historical anniversary watch from 1955.

Thanks to the dastardly thin Caliber 1003, measuring just 1.64 mm in height, the Historiques Ultra-Fine 1955 inches closer to the sub-four mm mark, but likely falls short due to the sapphire crystal case back – good eye candy perhaps, but adding unnecessary heft in a quest for supreme thinness.

Still, this is one tiny watch and the piece that finally breaks up a back and forth between two rivals we will be seeing more of as we progress down the list.

Quick Facts Vacheron Constantin Historiques Ultra-Fine 1955
Case: 36 x 4.13 mm, platinum or pink gold
Movement: manually wound Caliber 1003, 1.64 mm high, 31-hour power reserve, 18,000 vph/2.5 Hz frequency
Functions: hours, minutes
Price: $28,700 (pink gold), $37,300 (platinum)

6. Jaeger-LeCoultre Master Ultra-Thin Jubilee (2013): 4.05 mm

What’s this, another watch on this list outside of Piaget and Bulgari? Why, yes!

Back in 2013 Jaeger-LeCoultre celebrated its 180^th anniversary and decided to bust out an older movement from the 1990s, Caliber 849, and put it into a very slim case that made it one of the thinnest manual winding wristwatches in existence at a minuscule 4.05 mm.

This model continued the following year with a couple new iterations and it remains one of the thinnest watches you could ever have purchased from Jaeger-LeCoultre. Or anyone else.

Sadly, the movement and case have gone back into hiding and the current Ultra-Thin models are twice as thick (boo), so you’ll have to find this one on the second-hand market. Still, here is a fourth manufacturer popping into the battle for thinnest mechanical wristwatches in existence.

Quick Facts Jaeger-LeCoultre Master Ultra-Thin Jubilee Reference Q1296520
Case: 39 x 4.05 mm, platinum
Movement: manually wound Caliber 849, 1.85 mm in height, 36-hour power reserve, 21,600 vph/3 Hz frequency
Functions: hours, minutes
Limitation: 880 pieces
Price: €14,500 in 2013

5. Bulgari Octo Finissimo Tourbillon Automatic (2018): 3.95 mm

Jaeger-LeCoultre and Vacheron Constantin’s presence proves short lived on this list as we move to another Bulgari: the Octo Finissimo Tourbillon Automatic, which snatched up three records in one watch when it launched in 2018.

The Bulgari Octo Finissimo Tourbillon Automatic claimed the title for thinnest automatic watch, thinnest tourbillon, and thinnest automatic tourbillon – and very possibly ticked off Piaget to round things off. Coming in at just 3.95 mm, the Tourbillon Automatic even body slammed its own sibling, the aforementioned Octo Finissimo Tourbillon, by more than a millimeter.

Granted, it took three years of further development. But that just goes to show how committed Bulgari has been to constantly pushing the envelope of what most people think is possible in a watch as complicated as this.

Quick Facts Bulgari Octo Finissimo Tourbillon Automatic
Case: 42 x 3.95 mm, titanium
Movement: ultra-thin automatic Finissimo Tourbillon Caliber BVL 288 with 60-second flying tourbillon, 1.95 mm height, 32.6 mm diameter, 21,600 vph/3 Hz frequency, 52-hour power reserve, variable inertia balance
Functions: hours, minutes, seconds
Limitation: 50 pieces
Price: CHF 120,000

4. Historical Piaget Altiplano 9P (approx. 1964): 3.80 mm

And now we are back to Piaget, but this time another historical reference that mind-blowingly shows it is still one of the top four thinnest mechanical wristwatches – despite being nearly 60 years old.

This specific version comes from 1964, seven years after the iconic Piaget 9P debuted in 1957. This Altiplano measures a positively tiny 3.8 mm, edging out the Bulgari Octo Finissimo Tourbillon Automatic by little more than two hair widths.

Caliber 9P was often housed in thicker cases (out of practicality), but the impressive feat of creating a manual winding movement only 2 mm in thickness kept Piaget in the lead for thinnest mechanical movement until a few years later, when Jaeger-LeCoultre Caliber 839 (predecessor to the 849) was released in 1962 at just 1.85 mm.

Piaget set the bar high with the 9P and it became quickly recognized as one of the best ultra-thin movements ever made.

Quick Facts Piaget Altiplano 9P
Case: 31 x 3.8 mm, white gold
Movement: hand-wound Caliber 9P, 2 x 20.5 mm, 18 jewels, 19,800 vph frequency, 36-hour power reserve
Functions: hours, minutes
Year of manufacture: approx. 1964
Price: approx. €3,500 on the secondary market

3. Piaget Altiplano 900P (2013): 3.65 mm

Despite being the origin of ultra-thin for Piaget, the 9P still couldn’t pass our number three, the modern Piaget Altiplano 900P, which became the thinnest mechanical watch in the world when it arrived in late 2013.

The Altiplano 900P was the first modern Piaget to utilize the integrated case construction method for the movement. And since it didn’t need to add the automatic winding function found in the later 910P it was able to keep the height down by two-thirds of a millimeter over its younger sibling.

This is a very thin watch at 3.65 millimeters, and it seems as if it would be difficult to beat with any other method – or so Piaget thought. It lasted for two years as the thinnest mechanical watch in the world until it was usurped by our number two.

Quick Facts Piaget Altiplano 900P Ultra-Thin
Case: 38 mm x 3.65 mm, white gold
Movement: manually wound Caliber 900P integrated with the case, 48-hour reserve, 21,600 vph/3 Hz frequency
Functions: hours, minutes
Price: $31,400

2. Jaeger-LeCoultre Master Ultra-Thin Squelette (2015): 3.60 mm

Inching out the Piaget by the tiniest of margins during Watches & Wonders 2015 in Hong Kong, Jaeger-LeCoultre’s Master Ultra-Thin Squelette took Caliber 849 as a base, applied some fun skeletonizing, and then got even more aggressive with the case, shrinking the Master Ultra-Thin Jubilee down by a significant 0.40 mm.

This granted the Ultra-Thin Squelette the title of thinnest mechanical watch in the world (for a short time) and provides Jaeger-LeCoultre two spots in the top six thinnest mechanical watches of all time – while the battle rages on between Piaget and Bulgari.

This is the magic of Jaeger-LeCoultre: while the two tiniest titans continue to go head to head, JLC just slowly backs into the ring and tosses out a winner while the other two swing away at each other. The two probably didn’t even know what hit them until the dust cleared.

But, as always, Piaget had an ace up its sleeve.

Quick Facts Jaeger-LeCoultre Master Ultra-Thin Squelette
Case: 38 mm x 3.6 mm, pink gold and white gold with diamond-set bezel
Movement: manually wound caliber 849SQ, 1.85 mm height, 21,600 vph/3 Hz frequency
Functions: hours, minutes
Limitation: 100 pieces
Price: $58,500

1. Piaget Altiplano Ultimate Concept (2018/2020): 2.00 mm

Honestly, I would say this is more of a royal flush than just an ace as it doesn’t just squeak by Jaeger-LeCoultre and Bulgari’s case heights: it fundamentally obliterates them. The Altiplano Ultimate Concept comes in at a shadow’s width of only 2 mm. That isn’t only the movement; that is the case, movement, and crystal all squeezed into a height that practically disappears when you look at it from the side.

But this watch almost didn’t count, at least in the eyes of many. When it first debuted at the 2018 SIHH it was truly a concept watch and was so fragile that nobody was allowed to touch it. The press could only look at it and photograph it from a distance. Most doubted it would ever see the light of day as a production watch.

After two years of tweaking and adjustments, not to mention changing the material of the case to an extra-hard, super-rigid cobalt alloy, the Altiplano Ultimate Concept was finally released as a production watch (available for sale in in 2020), securing its spot as the thinnest mechanical wristwatch in the world in the eyes of everyone.

The odds are it may never be beat, at least in the near future, since it already is so incredibly thin that to go thinner provides no advantages and simply would be for the sake of setting a record.

Perhaps it has capped the race to the bottom, though only for a time-only, manual winding watch. There are still tons of categories that could be thinned out and squished into ever smaller case thicknesses. That may be where the records lie: with even more complicated watches. If we could see a chronograph under 5 mm or a grand complication under 6 mm it would surely be a feat to strive for that many would likely applaud.

Bulgari’s automatic Octo Finissimo Chronograph GMT has already gotten darn close at 6.9 mm in height . . .

Quick Facts Piaget Altiplano Ultimate Concept
Case: 41 x 2 mm, cobalt alloy, sapphire crystal 0.2 mm in height, flat telescopic crown
Movement: ultra-thin manual-wind Caliber 900P-UC, 28,800 vph/4 Hz frequency, 40-hour power reserve
Functions: hours, minutes
Limitation: 3 per year, by special order only, only available through Piaget boutiques
Price: on request

Authors note: I may have missed some watches, and there may be multiple Piaget models from history that match the thicknesses of the early Piaget pieces I have listed. If you know of any, feel free to share. This list is simply as accurate as the extent of my research and knowledge could allow. History is hard when you weren’t there!

You may also enjoy:

Piaget 12P: The Birth Of An Ultra-Thin Legacy

Bulgari Octo Finissimo Automatic: To Live With Is To Love

Ultra-Thin Head To Head: Jaeger-LeCoultre Master Ultra Thin Vs. Piaget Altiplano

Piaget Altiplano Ultimate Concept, The World’s Thinnest Watch: Shaving Microns To Make Millionths

Bulgari Octo Finissimo Chronograph GMT Automatic: Timing Is Getting Pretty Thin

Bulgari Octo Finissimo Automatic: Enchanting Ultra-Thin In Titanium, Gold, Ceramic And Now In Steel