How to Use Tachymeter Function on Watch Bezel – Usage Instruction and Definition

»»How to Use Tachymeter Function on Watch Bezel – Usage Instruction and Definition
On some of the analog watches or wristwatches from branch such as Omega and Casio, there is a outer scale bezel that inscribed around the rim and named tachymeter (also known as tachymetre or tacheometer). If you flip through the watch’s user guide or manual, you will not likely to find any explanation or definition on what is tachymeter or how to use the tachymeter functionality. Tachymeter is actually a tool used to compute speed based on travel time over a fixed distance traveled (like one mile or one kilometer). Thus, the tachymeter bezel or dial is a logarithmic scale (actually it’s not, as spacings between the marks on the tachymeter dial are proportional to 1/t where t is the elapsed time) that simplifies the computation of speed of an object, by computing the following function:

Tachymeter Dial = 3600 / Elapsed Time In Seconds

Tachymeter illustration

Depending on on the range of the scale printed on the bezel, tachometer timer normally works and valid for all elapsed times from about 7.2 seconds to 60 seconds, thus only able to measure speed greater than 60 miles per hour or 60 kilometers per hour.

To use tachymeter, simply start the chronograph or stopwatch when the object measured passing the starting line. When the object reaches the next mile or kilometer marker, stop the chronograph or stopwatch. The point on the tachymeter scale that adjacent to the second hand of the watch indicating the speed (in miles per hour or kilometers per hour) of object traveling between the two points.

For example, we want to measure the average speed of a vehicle is moving. Start the chronometer or stopwatch function when the car passes the starting line, and stop the timer after the vehicle traveled exactly 1 mile or 1 kilometer. Then look at where the chronometer hand (the second hand of the watch) is pointing to, and get the reading or value of the corresponding number at the tachymeter bezel or dial. Let’s say the stopwatch stop at 3 o’clock position, meaning 15 seconds had elapsed for the car to travel 1 mile or 1 kilometer. At 3 o’clock position, the tachymetre value shows that number of 240, which means the average speed of the vehicle was 240 mph or km/h.

Due to the limitation and constraint on the tachymeter scale mentioned above which makes tachymetre measurements works and valid only for certain range of speed, so in order to calculate and measure slower speeds or higher speed, user can decrease or increase the unit of measurement (e.g. change to half-miles or half-kilometers, or ten miles or ten kilometres). However, simple calculation is needed in order to get the correct average speed by using this technique. It’s also true if the length of the distance does not exceed a unit of mile or kilometer, or other unit which the speed will be based on.

For example, if we want to measure how fast the 200m athlete is running. Start the chronometer when the race starts, and stop the stopwatch when athlete crosses the finishing line. Let’s say the athlete used 20 seconds to finish 200m running, so according to tachymeter, the speed of the athlete is 180 km/h. However, the athlete only ran one fifth (1/5) of a kilometer, so we should divide 180 with 5 or 1/5 of 180, which mean the actual speed of the runner is 36 km per hour.

The above example can be used for object or thing that moving too slowly too, as when the object travels 1 mile or 1 kilometer, the duration would have exceed 60 seconds, the maximum limit of tachymeter. So the possible workaround is to measure the time taken for the object to move a shorter distance (such as 100m) and divide the tachymeter value with 10 (as 100m is 1/10 of a kilometer).

What if the object travels too fast, such as a rocket or plane. In this case, user can increase the units of the distance covered by the object to measure a longer period of time so that the duration is greater than at least 7.2 seconds (typically the lower limit). We can measure the time taken by the object to cover 10 miles, let’s say it took 30 seconds, so the tachymeter will tell us the the speed is 120 miles per hour. However, 10 miles have been traveled, so that actual speed is 120 times 10, which is 1200 mph.

Wikipedia also explains that function performed by a tachymeter is independent of unit of distance (i.e. is not specific to miles or kilometers). A tachymeter can be used to measure speed in nautical miles per hour or meters per hour, or to measure an industrial production process in units per hour. A tachymeter is simply a means of converting elapsed time in seconds per X to X per hour.

By | 2016-12-09T08:40:54+00:00 December 9th, 2016|Categories: Miscellaneous|Tags: |61 Comments

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LK is a technology writer for Tech Journey with background of system and network administrator. He has be documenting his experiences in digital and technology world for over 15 years.Connect with LK through Tech Journey on Facebook, Twitter or Google+.
  • Very nicely explained! Exactly what I was looking for

  • Oleh

    thanx for great explenation!
    Now i understand how to use it.

  • walo

    gracias por tu explicacion yo tengo un casio edifice 503 y en el manual no especifica nada sobre el tachymeter ahora ya lo se y me pondre como loco calculando todo jaaa salu2 desde lima peru

  • Thank you. I have a Casio Edifice and I didn't know what it was and how to use it. I do now. Thanks again!

  • Anoop Menon

    I bought a Titan Octane… And this article helped me a lot.

  • george

    Thanks for explain , it is very useful for me

  • Sandeep

    Thanks for explaining this , but what is the use of North , south etc..on the tachymetre

  • Alwin

    I got the information that i need.
    I got a clear idea.

  • Bob Vickers

    Great thanks, understand now, explained very well.

  • mukund was very infomative…

  • Pratheesh

    for to calculate speed ,we do not need tachymeter.speed=distance/time.can we calculate speed in tachymeter without knowing the distance?????

  • Swetank V Telang

    I have bought a Rolex chronographe tachymeter and this article has helped me a lot in understanding the concept of a tachymeter.

  • thanks i found this information to be useful for my tagheuer watch.

  • Santosh

    Thanks a lot…

    I am using a CASIO Edifice EF539, & this article have helped me to understand my watch's usage.

    Cheers 🙂

  • Albert

    I am using a JACQUES LEMANS F5023, & this article have helped me to understand my watch’s usage.

  • Sabu


    I was atleast able to differentiate the meaning behing those words:

    1. Chronograph
    2. Tachymeter.

    Since i am using Swistar Chronograph watch

  • Max

    I have a 10 ATM Fossil watch that my grandma gave me and i was wondering what the thachymetre was for and this article was really helpfull.
    Thanks. 🙂

  • david

    always wondered how tachometer works, now I know. thanks

  • mayank

    the article is informative, but do we need a tachymeter to calculate speed. i mean it does nothing but calculates time. it would have been better if it could calculate without knowing the distance.

  • Vikram

    Excellent explanation.. Thanks a lot pal.. B-)

  • Fahad

    i am using casio edifice 539 ad and this article is very useful to me, thanks a lot.

  • Rick

    Thankyou I just bought an AquaSwaiss watch with the tachymeter and it helps me to understand it. You are the only one who explains it.

    Rick Felty

    Tacoma Washington

  • Juvever

    This helps. Thanks for explanation.

  • Peter Kornum

    one question…. do the same scale work for both km and miles?? or is there two scales? and if there is haw do i reconize the km one?

  • Sheraz

    I m using Titan Orion and this article helped me alot.thanks

  • Sheraz

    I m using titan orion and thia topic helped me aloy in understanding the concept of tachymeter

  • Dave

    Great – thanks! Just got a new watch and it had been really bugging me not knowing what those numbers were for. Would have been so hard for them to put this explanation in the instruction book?!

  • Tahir

    Sorry, I couldnt understand how to use this function in my watch, I just bought a TITAN9244QAA with tachymeter function, but i dont know how to use it. Can you help me in this specific TITAN case

  • kozi

    This is good news. I have been wondering how I was going to explain the use of tachymetre to any one. my tissot has got one.

  • Jason

    i just bought a BUM Sport Watch and i wander what can the tachymetre do for us. Now, i can tell my friends that the way to use the tachmetre proudly. Thanks alot.

  • Vivek Sadhwani

    The Info was great. I work in watch boutique but no one knew about this, not even my manager who's working there for 17 yrs. Thanks a lot for publishing it.

  • Ali Aziz

    The explanantion of Tachymeter and the technique to make use out of it is a great help. I really appreciate it.

  • ranald casper

    Thank you very much i bought a new timex t49803 and it helped a lot

  • Karma

    Thanks a lot for the info ….. took me all these yrs to find out … but….. better late than never …

  • Raj

    I first came across this term around 1990 and back then did not find much info about it. Last week, I was gifted a GUESS watch which had tachymeter on it and thanks to your article, I now know what it is.

    Thanks a lot.

  • ajek so

    just get myself a new watch with tachymeter bezel. and the 1st thing i do is google it. 🙂

  • Tboi

    Thks, just bought a Timex with a Tachymeter and was wondering how to use it….good info

  • Kenneth

    Got myself a Chronograph with Tachymeter but wasen't able to figureout how to use the Tachy function. Thanx for the help!!!! Nice Post! 🙂

  • donald

    it really helped a lot…i brought a quartz rosra…which have a tachymeter.

  • disturbedone

    Very helpful.
    just bought the Casio Edifice 305D. Nice piece.
    Thanks alot.

  • Piaget Watch

    Good resource of information..continue to keep it up 🙂

  • lolo

    Two questions: How do you measure if it took over 60 seconds to make a mile? Also, why doesn't the bezel move? You can't expect to synch the start at the top of the dial. It's hard to figure when the subject hits a mark 18 seconds after 12, then subtract 42 seconds from everything, and then factor in it took 72 seconds to make a lap.

  • Toofan Singh

    There are many thing around us about them very few peope know, but they carry lots of knoledge just waitig to be explored. This is one of then, Very Informative.


    Great explanation about tachymeter now i can explain to my customers.

  • ali

    thanks a lot

  • Hisham

    really thanks , never thought it is that easy or me that idiot 😀

  • Chaq

    Thank you for your concise and erudite explanation of the tachymetre function 🙂

  • Gustavo Adolfo

    Mil y mil gracias por la explicación,

    ha sido muy práctica y a partir de ahora… útil!

  • Mícheál Furey

    Thanks for this; it was recommended by a guy at Accurist’s helpline. His colleague was trying to figure out why my new watch was described as having a tachymeter when that function had no moving parts. I think I understand this function now; though I might need some remedial classes in the near future.

  • masoud

    this is a good explain about tachymeter.thank you for it.

  • Udit

    Explained in a very simple manner which is easy to understand and to use in an everyday situation.

  • Thanks

    Well done, great explanation. Thanks to the author for this article.

  • ck

    very good and simple explaination. thank you.

  • Jimbo

    How does the tachymeter relate to units of laffy taffy. Is there a simple mathematical equation, or is it like complex and stuff?

  • hasan

    hi very very thank for your best explain I very happy because now I know what is this in my watch . \
    Hasan Hojati from : Iran


    thank you.
    i was really wondering what is tachymeter in my casio-edifice presented to me
    by friend Mr.Vijayaraghavan. i was hesitant to ask him direct. thanQ again.

  • Bouch

    Thanks, now I know what this thing is on my watch that is useless and never be used.

  • viral

    thanks a lot buddy…


    very good explanation,,,,,,,,,,,,,,,,,thank you

  • farzan

    best explanation

  • fucker

    fuck u