How big is that gadget? Pective can tell you.

Scale is a tricky thing to capture in pictures. Cereal boxes "enlarge to show texture." National Geographic crams sweeping vistas onto average magazine pages. And, gadget ads in particular can have a rear-view-mirror quality to them, tricking us into thinking that new gear is bigger (or smaller) than it appears.

For example, Gizmodo gave Apple a hard time last year when the company released a new iPhone ad. The promotional shot made the smartphone look much smaller than before – turned out that they simply hired a model with larger hands.

Pective.com tries to dispel any doubt about the true size of things. The website displays pictures of products and then scales them to their actual dimensions. Start out by telling Pective the size of your screen, then click through oodles of hand-helds, foreign coins, rulers (inches or centimeters), and even weird items such as 2008 Olympic medals and a golf hole.

I just recommended Pective to someone here in the office who's been eyeing Amazon's Kindle ebook reader, but has never seen one in the wild to get a sense of scale. Now that she knows it will fit in her purse – we actually held up her purse to the screen – she plans to pull out her credit card and order one tonight.

Webware's Josh Lowensohn suggests using Pective to compare cell phones to your current model. And one cheeky user posted a picture of the 800-foot Hindenburg airship. Needless to say, my 20-inch screen didn't quite do it justice.

If one of the pictures looks off, you can comment that the scale seems too big or too small and the site (designed by programmer Pratham Kumar) will work to find a happy Goldilocks medium.

My one complaint is that while the site does a great job with small or tall gadgets, it cuts off large and wide items. An image of a full keyboard looked spot on, but I couldn't see more the left third because the site only lets you see 600 pixels at a time. You have to scroll through the rest. But, hey, who cares – it's free.

You can add your own pictures to the database. It'll ask for the URL of a photo (Pective won't upload photos, it borrows them from other websites) and then the dimensions of the object. The process takes about a minute.