> ## Knowledge Base Index > Fetch the complete knowledge base index at: https://clockworks.crisp.help/sitemap.xml > Use this file to discover available pages before exploring further. > Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash). # The Mechanical Clock Pendulum Length ### The mechanical clock pendulum length A pendulum clock without a [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) is a shame for sure. Hence, getting the mechanical clock pendulum length correct does take some diving into the clock world. If there is no idea what [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) it would take, this is a basic guide. Of course, this is a basic guide to narrow it down to the best pendulum for the clock. This will cover most situations, without special equipment to figure out the length. [![](https://storage.crisp.chat/users/helpdesk/website/-/9/5/9/1/9591a3f915bf7800/pendulums_p60qz8.jpg =857xauto)](https://www.clockworks.com/clock-parts/clock-pendulums.html) ### Click on the picture to shop Clock Pendulums on Clockworks.com ### The movement CM or PL stamp On the back plate of the clock movement usually, there are some numbers and or letters for identification. Likewise, there may be an indication of how long the pendulum should be in the mix of these numbers. It may say CM or PL and this stands for [centimeter](https://en.wikipedia.org/wiki/Centimetre) or [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) length. Subsequently, this would be the length where it should keep approximate time. Generally, there are a few different ways to measure this depending on the country of origin. ### Mechanical Clock Pendulum Length for German made movements Most mechanical German made clock movements are easy to figure out the pendulum length. In essence, the numbers will let us know or the stamp will clearly state the CM or PL number. If it is German, keep in mind the CM length is not the actual pendulum length. Altogether, German units measure this length from the top of the clock movement, and this includes the three components of the pendulum all in one length, in [centimeters](https://en.wikipedia.org/wiki/Centimetre). This length will include the [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) itself, the [leader](https://www.clockworks.com/product/clock-pendulum-leader) that it hooks to, and the [suspension spring](https://www.clockworks.com/product/clock-pendulum-suspension-spring) on the top that the [leader](https://www.clockworks.com/product/clock-pendulum-leader) hooks on to, all in one CM measurement. To clarify, CM stands for centimeter and PL stands for pendulum length. [![](https://storage.crisp.chat/users/helpdesk/website/-/9/5/9/1/9591a3f915bf7800/leaders_nk48ao.jpg =319xauto)](https://www.clockworks.com/product/clock-pendulum-leader) ### Click on the picture to shop Pendulum Leaders on Clockworks.com [![](https://storage.crisp.chat/users/helpdesk/website/-/9/5/9/1/9591a3f915bf7800/suspension-springs_1ytkmue.jpg)](https://www.clockworks.com/product/clock-pendulum-suspension-spring) ### Click on the picture to shop Clock Suspension Springs on Clockworks.com ### If no stamp try to convert When there is no stamp with the CM on the movement, there are some additional steps that need to happen. You will need to cross reference The [numbers on the back plate](https://www.clockworks.com/clock-movement.html) to the pendulum length that you need. The first step is to [identify](https://www.clockworks.com/clock-movement.html) the manufacturer of the clock movement by using the movement numbers. The movement numbers indicate who the actually manufacturer is of the movement. Various clock retailers may have a stamp of their name on it, but the numbers are always true to the manufacturer. ### Converting numbers to CM length Moreover, some movements do not have an indication of the pendulum length on the back plate. The unit will have a number that would need to be found on this website first to find out what the correct CM length is for it. ### Conversion number example Generally speaking, let's say that the movement has no CM stamp on the movement and only shows the [Urgos](https://www.clockworks.com/clock-movement/urgos-clock-movement.html) number [UW32319](https://www.clockworks.com/product/uw32319-urgos-clock-movement). Go to the [identification page](https://www.clockworks.com/clock-movement.html) to look at the movement number examples. In this example, we see that it is a [Urgos](https://www.clockworks.com/clock-movement/urgos-clock-movement.html). Now it is possible to go to the [Urgos](https://www.clockworks.com/clock-movement/urgos-clock-movement.html) page and find the number to see what the pendulum length is. In this example, the pendulum length would be 80cm, representing the full length with the size including the size of the [bob](https://www.clockworks.com/product/mechanical-clock-pendulum-bob). [![](https://storage.crisp.chat/users/helpdesk/website/-/9/5/9/1/9591a3f915bf7800/hermle-mvmnt-identify_1na4p6k.jpg =1005xauto)](https://www.clockworks.com/clock-movement.html) ### Click on the picture to learn about Mechanical Movement Identification on Clockworks.com ### German grandfather movements Almost all [grandfather clock movements](https://www.clockworks.com/clock-movement.html) are going to be German if made after 1950. The first thing we need to do is get the numbers off of the back plate of the movement. This is the only way, and we can't cheat by looking at the paperwork or clock case. It has to come right off the back of the clockworks. The manual and the sticker on the case is of no use to get the pendulum. ### American clocks The American mechanical clock movement manufacturers refer to the [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) length as a "drop". The drop is the length of the pendulum from the hand shaft all the way down to the bottom of the pendulum [rating nut threads](https://www.clockworks.com/product/clock-pendulum-rating-nut-and-threads). It is a different way of measuring the [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) length then the German made way. The basis for both ways are on the smallest [bob](https://www.clockworks.com/product/clock-pendulum-bob-for-a-wood-stick) diameter. If the bob is larger or heavier, the length would be longer than what the stamp indicates. ### No luck If everything fails for one reason or another, the best chance for a [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) is the [wood stick](https://www.clockworks.com/product/wood-stick-pendulum-for-hermle-clocks) style. This is the only style of pendulum that can be easily modified because it can be cut down. These types of clocks are usually antiques, or of Asian origin, and information such as pendulum length is simply not available. Sometimes it takes a good guess on where the manufacturer meant to have the bob sit. To do it this way, you only need a [pendulum](https://www.clockworks.com/clock-parts/clock-pendulums.html) with a stick that is way too long to begin with. Chop it, try it, chop it, try it. Each time slowly cut an inch and half off of the sticks length and hang it back on. It will only take a couple of times, and if starting way too long it can always go shorter. ### Clock makers method for Mechanical Clock Pendulum Lengths There is another way, which is known as setting the beat rate. This is a more complex way and is usually just done by [clock makers](https://www.clockworks.com/about-clockworks.html). It involves a beat detecting device that counts out the beats per hour, or the beats per minute. To do this, first figure out what the beat rate is suppose to be for that particular movement. Then keep adjusting the pendulum length until it keeps time. There are cell phone apps out there these days that will tell the beat rate and the cell phone will listen and say if the clock will keep time with that pendulum. Go longer or shorter until the phone says the beat rate is set. ### Contacting us for help with Mechanical Clock Pendulum Lengths Please email the movement numbers from the back plate, and explain what part you need. The email address to send this information to is clockworks@clockworks.com. We always welcome pictures but they are not a necessity. If emailing pictures please include the back side of the clock movement where the markings are. *The content of this website is copyright by [Clockworks Inc.](https://www.facebook.com/ClockworksUSA)