Not sure what size lens cap you need? The measurement you’re looking for is the diameter of your lens, often called the filter size. This isn’t the same thing as your focal length (e.g., a 50mm prime lens or a 70–200mm zoom lens), the millimeter figure you probably do know, so be careful not to confuse the two. The diameter is the distance across the front-most part of the lens. No need to bust out the calipers, though, as the number is quite likely written right on the outside of the lens, marked with a diameter symbol (ø). Here's how it looks on Corrie’s lenses:
If it isn’t printed so clearly in white text, try looking for lightly etched numbers. If it isn’t written anywhere on the lens, pull out the user manual or check the manufacturer’s website for the specs. Worst case, you may need to pull that ruler out of your desk drawer after all and measure from the inside rim on one side to the inside rim on the opposite side.
The most common lens cap sizes (and the ones we carry) are 52mm, 58mm, 62mm, 67mm, 72mm, 77mm, and 82mm. If your lens happens to have a different diameter, though, send us an email, and we’ll see what we can do!