Editorial policy

An undersized wire does not fail on day one. It runs warm for years.

That is the whole reason WhatSizeWire exists. We would rather show you one number you can trust, and exactly how we got it, than ten numbers you have to second-guess. Here is how we work.

We show our working

Our calculator pages show the formula behind the answer, so you can do the math on paper if you would rather. Where a result depends on published data, such as a standard size or a typical weight, we link the source, and we keep adding step-by-step worked examples. If our answer and yours disagree, one of us has made a mistake, and we want to know which.

We test before we publish

Every wire size, voltage drop and conduit fill figure traces back to the published resistance and ampacity tables, not to a rule of thumb. Right now WhatSizeWire has 7 calculators and 13 automatic checks. Each check is a hand-worked answer the calculator has to match exactly. They run every time the site is updated, and an update that breaks one does not go live.

Tables first, then the math

Ampacity and voltage drop come from published tables and conductor resistance. Code rules vary by edition and location, so treat a result as a planning figure and check it against the code your inspector uses.

Dates mean something

The "Updated" date on a page only changes when the page itself changes. We do not bump dates to look fresh.

Ads pay the bills, not the answers

WhatSizeWire is free to use and is meant to be supported by advertising. Advertisers never see or influence our numbers, and we do not sell links, sponsored rankings or paid reviews.

Tell us when we are wrong

If a number looks off, send us the page and the value. Hassan Nawaz reads every message. Confirmed mistakes are fixed, the page date is updated, and if your note made a page better, we are grateful for it.

Hassan Nawaz
B.Sc. Electrical Engineering, WhatSizeWire