You'd think that an aspiring baker who ordered five 9-inch pie plates from five different manufacturers would be able to cook five pumpkin pies that were exactly the same size. Not necessarily.

Measurements listed on retailers' websites aren't uniform, and they are not always reliable. Here at Wirecutter, this is a frequent challenge for us. The specs for something you see on Amazon don't always tell the full story. For instance, regarding those pie plates, senior editor Marguerite Preston knows that 9 inches could refer to the diameter of the base of the plate, to the top inner edge, or even to the top outer edge -- 9 inches doesn't necessarily mean the same thing to everyone.

That's why Wirecutter writers and editors often take measurements into our own hands. We do our best to suss out important specs so readers know exactly what they're buying.

Fractions of an inch may not seem like a big deal, but the geometry of a pie plate is crucial data. "For the purposes of baking pie, that's important because you want to have enough space to flute the crust," Marguerite says. Most crust recipes are perfect for pie plates that are 9 inches in diameter from the inner edges, as Marguerite explains in our guide to the best pie plate. Because there's no standard across the industry, our expert journalists even tested some dishes that were not 9 inches, to be sure they were evaluating all possible options.

Senior staff writer Jackie Reeve applies the same logic to textiles. She keeps a large measuring board, similar to this one, on her sewing table and uses it to determine the length and width of all the sheets, blankets, and towels she reviews for Wirecutter. She then washes the fabrics and measures again, noting which kings and queens end up shrinking.

This process is not perfectly scientific, but she says that the way textiles change shape over time is important information because people will be living with these items for years. It's especially important for sheets. "Most sheets shrink, and that can change the way they fit on your bed over time," she says.

There's often a discrepancy between our data and what's listed on the manufacturer's website or the box something comes in. Senior staff writer Doug Mahoney, who wrote our guide to the best power drills, found that "there are three weights floating around for each drill: There's the drill body alone, there's the weight of the drill with a battery, and there's the shipping weight."

Since most people prefer lighter drills, manufacturers often list the weight of the drill body without the battery included, even though it would not be functional as a drill without the battery. When you finally get around to hanging that gallery wall in your living room, a heavier-than-expected drill can mean the difference between a finished project and a sore arm.

When Doug made a chart of nine drills and their weights, he found there was only one instance where his measurement, the manufacturer's measurement, and the retailer's measurement were all the same. A retailer's weight could be up to 2.2 times heavier than Doug's measurement, probably because the retailer was including the packaging the drill was shipped in. Usually, however, the sellers' listed weights for these drills were roughly half a pound too low, likely because they weren't including the batteries.

Doug included the battery in the drill's weight because he wanted people to have the most helpful information when they were determining which tool they'd rather use for hours as they fixed a fence or built a beehive. "I weigh and measure things that might have inconsistency or where I think it's very, very important to the tool's success or failure," Doug says. "Like screwdrivers, they're all pretty manageable. Drills we weighed, because that is a crucial measurement."

Light and color might seem more difficult to quantify. But senior staff writer Dave Gershgorn took a class in display calibration in order to learn how to do exactly that. He regularly rules out computer monitors he tests because their brightness, contrast, or color accuracy do not line up with our standards, even if, going by the manufacturer's information, they do.

In order to make these measurements, he uses a spectrophotometer, a colorimeter, and software called Calman. "Very simply, this computer program sends a series of colors to the display, and the hardware looks for the difference between the color it sent and the color it sees," he says. "We can use this to measure tons of aspects of the monitor, and gauge its relative quality."

These details might seem small. After all, there are many more factors that go into the perfect pie plate than its diametrical precision.

But if it's not the right size, none of the other stuff will even matter.