About and methods
Size and Spec answers one question well: how big is it? Each of our 204 pages gives the measurement first, draws it to scale and shows where the number comes from.
Where numbers come from
We start from the document that defines a size: ISO 216 for A-series paper, ISO 668 for shipping containers, ISO 6780 for pallets, the American Softwood Lumber Standard (PS 20) for lumber, ASTM D1785 for PVC pipe and the official rulebooks of IFAB, FIBA, ITF, FIVB, BWF, USA Pickleball and the NFL for sports.
Where a size is pure geometry, such as a TV screen from its diagonal and aspect ratio, we calculate it exactly rather than copying rounded figures.
Where sizes are conventions rather than standards, such as shoe sizes or bed frames, we say so on the page and give the range you should expect.
Units and rounding
Every conversion uses the exact definitions: 1 inch = 25.4 mm, 1 pound = 0.45359237 kg and 1 U.S. gallon = 3.785411784 liters. We round only when displaying a number, and fractions of an inch are given to the nearest 1/16.
Drawings are to scale within each picture, using a 5 ft 9 in (175 cm) person or a credit card (85.6 × 53.98 mm) as the reference.
Corrections
If you find a number that does not match its source, send us a note with the page and the source you are using. We check every report and update the page and its “last checked” date.