About AmpSize

AmpSize is made by one person in New Zealand: an industrial electrician who moved into software and kept sizing cables.

Why it exists

For years I sized cables the slow way: the standard open on the bonnet, a calculator, and a page of working. Then the working moved into a spreadsheet. Then I started writing software, and the spreadsheet started to bother me.

A spreadsheet gives you a size. It does not show the table the rating came from, the factors it applied, or the clause that set the limit. Those are the parts an inspector asks about, and the parts an apprentice needs to see. Every AmpSize result shows its working and names its table and clause, on the page, next to the number.

I like calculators. A good one moves what one trade knows into a form another trade can use, and the working travels with it.

Where the numbers come from

The current ratings, impedances and correction factors are encoded from the tables in AS/NZS 3008.1.1, AS/NZS 3008.1.2 and AS/NZS 3000, and checked cell by cell against the printed standard. Each table on the standards page says whether it is verified or derived, and a derived value is marked as derived wherever it appears.

AmpSize cites table and clause numbers. It never reproduces the text of a standard, and it does not replace one. It is a design aid, and the person who signs the work still checks the result.

How it is built

Every calculation runs in your browser, and the values you enter sit in the page URL so a result can be shared or bookmarked. There are no analytics and no tracking. The site and its database run on Azure in Australia. Every calculator is free; the Pro plan adds saves, projects and branded PDF reports, and pays for the hosting.

Get in touch

If a number looks wrong, name the tool and the table and I will check it against the book. Questions, corrections and requests for a calculator that does not exist yet all go to hello@ampsize.nz.