How we size

Each tool follows rules that someone accountable has published. Most come from the people who make the product, such as Wilson's glove guide or Osprey's torso chart. Others come from specialist retailers like REI and evo, and from standards and professional bodies, such as the ISO glove size table and the American Podiatric Medical Association.

Across the 18 tools, we cite 99 pages from 78 different websites. Every tool page lists its sources at the bottom, with links, and the full list is at the end of this page.

An answer has three parts. Take a rug for a bedroom with a queen bed, which is a real case from the rug tool.

1. The rule

   The published bedroom guides agree that a queen bed takes an 8 x 10 ft rug, so that is the answer.

2. The judgment call

   The same guides do the arithmetic for how much rug shows around the bed differently. We follow the size they agree on and use the math only to check that the rug fits your room.

3. The caveat

   Real rugs often measure a few inches less than the size in their name. The answer says so, and tells you to check the listed dimensions.

When you fall between two sizes, the answer can name the other size and say when it is the better pick. When your numbers cannot produce a sensible answer, such as a room too small for the bed, the tool says that instead of guessing.

• We search Amazon for each size and keep only products whose Amazon listing confirms that size. A product with a missing or different size does not appear.
• Each product model appears once, even when Amazon lists it in many sizes and colors. The cards keep the order that Amazon's own search returns.
• Prices are checked at least once every 24 hours. Every list shows the time its prices were read, and the price on Amazon at checkout is the one that applies.
• No brand or seller pays for placement, and no product appears because someone asked us to list it.
• We earn a commission from Amazon when you buy through our links. As an Amazon Associate, we earn from qualifying purchases. The commission is a small percentage of the price, usually 3% to 4%. It costs you nothing extra, and the order of the cards comes from Amazon's search, not from the commission.

• We never promise that something will fit. Brands cut and label sizes differently, so an answer is a well-sourced starting point. Check the size chart on the product page before you buy.
• We never give temperature, warmth or safety advice. The sleeping bag tool, for example, sizes bags by length and width only.
• We do not cover safety equipment, such as helmets, climbing harnesses, life jackets and baby car seats. A wrong size there can hurt someone, and a website cannot check the fit.
• We never give medical advice. The kids' shoe tool finds a shoe size. If a child's foot hurts, ask a doctor.

If an answer looks wrong, tell us. Send the link to the tool page, because it carries the numbers you entered, and say what you expected instead. We read every report.

Email your report.

Each tool cites the pages below. The same list, with links, sits at the bottom of each tool page.

Who runs Sizemaven and how it earns money is on the about page.