You probably have a watch (like the Voyager or the Explorer) that has a weird, busy looking bezel that has a ton of markings and numbers. This is called a Slide Rule Bezel, and believe it or not, it can be used for simple calculations, some of which may prove to be nifty when traveling abroad. Sure, you could whip out your smart phone to do a calculation or conversion, but it may be quicker and more convenient to do it on your wrist. Spare your battery power and use your slide rule with extremely simple steps.

Note: The slide rule uses the number “10” as a base unit, and conversion is performed in multiples of 10. On the inner bezel (or fixed bezel, the ring that does not move), “10” is usually highlighted with red. While the slide rule is used as a reference, it’s important to use common mathematical sense, like knowing that 20 x 16 will be a three digit number, and not two.

Multiplication

Let’s say we want to multiply 25 and 14.

1. Rotate the bezel so that “14” on the outer ring matches up with the base 10.

2. Locate “25” on the fixed ring, and you’ll see that it is lined up with “35” on the outer ring. This tells you that 25 x 14 is 350.

Currency conversion

This is extremely helpful if you’re traveling in a foreign country. Let’s say you want to convert 20 US Dollars to Euros. At the time of writing, the exchange rate is 1 USD to 0.88 Euro.

1. Rotate the bezel so that “88” on the outer ring matches up with the base 10.

2. Locate “20” on the fixed bezel, which is lined up between 17.6 and 17.8. The actual conversion would be 17.69 Euros.

Distance conversion

Distance conversion is also extremely helpful when being abroad, especially if you have to convert statute miles to kilometers and/or nautical miles. Let’s convert 20 statute miles.

1. Rotate the bezel so that “20” on the outer ring matches up with “STAT” on the fixed bezel.

2. To find the nautical miles and kilometer conversion, find the “NAUT” and “KM” markings on the fixed bezel, and see where they line up with markings on the outer ring.