The pupillary distance (PD) measurement is a requirement for people who want to purchase eyeglasses. Here, find out how to measure your PD using a mirror and a ruler. Share on Pinterest Some eyewear ...

Smartphones are useful for a lot of things. You can even use one as a ruler in a pinch. Generally speaking, you won’t replace your trusty yard stick. A phone is simply too small for anything other ...

Pupillary distance is the space — measured in millimeters (mm) — from the center of one pupil to another. When you need glasses, an optometrist or an optician will measure this distance to make sure ...

Measure with centimeter cubes to find the length of reptiles. Add & subtract within 100. Warm up with a Mystery Math Mistake as you add two 2-digit numbers using a decomposition strategy. What do you ...

What you need: ruler, protractor, pencil and paper. Use these to construct a triangle when you know the length of 1 side and the 2 angles at each end of it. In this case use the length 8 cm, and the ...

A revolutionary kind of laser light called an optical frequency comb makes possible a more precise type of atomic clock and many other applications Editor's note: This story was originally posted in ...

The best way to measure your feet for running shoes is by heading to the shoe store and getting fitted by an expert. But if you need to troubleshoot sizing on your own, all you need is a ruler, paper, ...