Stitch Math is an independent reference site for knitters and crocheters. It exists to answer three questions with arithmetic rather than guesswork: how many stitches to cast on, how much yarn a substitution needs, and which needle or hook a size refers to.
Where the numbers come from
Size and weight conventions follow the Craft Yarn Council industry standards: the Standard Yarn Weight System, Hooks & Needles, Steel Hooks, Wraps Per Inch and the body measurement charts. The CYC publishes metric and US sizes and advises makers to rely on the millimetre measurement, which is what this site does.
Yarn records in the library are factual specifications: put-up, fibre percentages, recommended gauge and tool sizes. Each record carries the date it was checked and links to the manufacturer. Where a yarn is sold in more than one put-up, the standard skein is recorded and the variation is noted.
We do not reproduce manufacturer descriptions, pattern text or product photography. Diagrams and still-life illustrations on the calculator and reference pages are drawn for this site; photographs on the guides are licensed from Wikimedia Commons and credited on the photo credits page.
How the calculators work
Every tool page prints its formula. The arithmetic runs in your browser in plain JavaScript; nothing is sent to a server, and there is no account or saved history. If a result looks wrong, you can reproduce it by hand from the formula shown on the page.
Calculations are estimates. Gauge, ease, fibre behaviour and blocking all affect the finished object in ways arithmetic cannot capture. Always swatch, and always check the label on your skein.
Editorial independence
The site does not accept payment for inclusion in the yarn library or for placement in a guide. If affiliate links are added in future, they will be labelled, and they will not change which yarns are recorded or how they are described.
Corrections
Yarn specifications change, and manufacturers sometimes reissue a line with a different put-up. If a record disagrees with the label on your skein, the label wins. Please send the correction with the yarn name, the figure you believe is right, and a photo of the label if you have one.
Who runs this
Stitch Math is a small independent project. It is not affiliated with any yarn manufacturer, publisher or retailer. The site is funded by its own operating budget.