Privacy

Analytics and cookie choices

We use Plausible and Google Analytics 4 to understand which pages and tools people use. They receive page-view information and general actions, such as using a calculator, opening a result or downloading a file.

These requests include browser and connection information, including your IP address. We send Google a page address without its query string, fragment or referring address.

Plausible measures visits without cookies and can report time spent and scrolling. We send it a page address without its query string or fragment. It also receives the referring page address when your browser provides one.

Your project measurements, calculator entries and worksheet values are not included in the action information we send.

Plausible counts every visit without cookies. It may receive browser and device information and a referring page.

Google Analytics is run by Google, which receives the page address, the actions we measure on this site and browser and device information, and sets cookies that tell repeat visits apart. Its advertising features are off.

In the European Union, Iceland, Liechtenstein, Norway, the United Kingdom and Switzerland, and whenever we cannot tell which country a visit comes from, Google Analytics loads only after you choose Accept on the bar at the bottom of the page. Decline loads nothing from Google. Your choice is kept in this browser for six months, then the bar asks again.

Elsewhere, Google Analytics loads with each page unless you choose Decline. Cloudflare, which delivers our pages, tells your browser which country the visit comes from.

Wherever you are, Cookie choices at the bottom of any page, or the button below, changes your choice. Decline stops Google Analytics on this site in this browser and deletes its analytics cookies. If analytics was running, the page reloads to apply your choice. Decline holds on every page; outside the countries above it is kept until you change it.

Cookie choices

Cookies and local storage

This site sets no advertising cookies and no cross-site tracking cookies.

Plausible is cookieless: it counts visits without storing an identifier on your device.

Google Analytics sets cookies that tell repeat visits apart, only where it is allowed to load, as described under Analytics and cookie choices above. Its advertising storage stays off everywhere. Your Accept or Decline is kept in this browser, in a cookie of this site and in its local storage, for six months.

A few features save in this browser’s local storage: the chart you draw in the chart maker, your place in a lesson, the instructions you tick in a pattern and the row counter’s count. They stay on your device, they are not cookies and they are never sent to us. Clearing this site’s browser storage removes them. Calculator entries are not stored there; they live in the page address, as described below.

If you are in the EU, the EEA or the UK

We rely on legitimate interests for Plausible’s cookie-free count of which lessons and tools are useful. Google Analytics sets cookies, so here it loads only after you choose Accept on the bar at the bottom of the page; Decline loads nothing from Google, and Cookie choices at the bottom of any page changes your answer.

Our measurement and hosting providers sit outside the EEA. Google LLC (Google Analytics, after you accept), Amazon (product photographs and product links) and our own Plausible instance receive connection information, including your IP address, when a page or an image loads. Google states that it relies on the EU–U.S. Data Privacy Framework and on standard contractual clauses for its transfers out of the EEA.

You can ask what we hold about you, ask for it to be deleted, or object to this measurement. We hold no account, no mailing list and no identifier for you, so unless you have sent us a report the practical answer is usually that there is nothing to return. Use the contact page and we will answer.

If a display advertising network is added to this site later, it will bring its own vendors and its own consent request, and this page will say so before that happens.

The other companies involved

Cloudflare routes and protects the domain, runs the security check on our contact form and keeps reports sent through it. Discord holds a copy of each report in a private channel our team reads. Plausible Analytics, our own instance, measures page visits. Google Analytics measures page visits and tool actions where it is allowed to load, as described above. Amazon serves product photographs at page load and receives the request when one is displayed, and records the referral when you follow one of our supply links, which is how the site is funded.

Nobody else is involved: there is no advertising network, no email provider, no comment system, no embedded video and no font service, because the typefaces are served from this domain. Following any supply or source link opens a site with its own privacy practices; no purchase is processed here.

Calculator and worksheet inputs

Calculators and the substitution worksheet run in your browser. We do not upload their inputs or save them in cookies or browser storage. Downloads are created locally when you choose to export.

Calculators keep your current entries in the part of the page address after #, so a reload keeps them, and links between the worksheet and the quantity calculator carry them the same way. This stays in your browser, but sharing that address also shares those entries. Remove the # part and reload to start with the examples again.

Manufacturer links

Manufacturer and shop links open services with their own privacy practices. Amazon links carry our affiliate code, which tells Amazon you came from this site and can earn us a commission at no extra cost to you; the affiliate disclosure page explains this. We do not receive your order, payment or account information.

Product photographs

Where a supply photo is available, your browser requests it from Amazon’s image service. That service receives the network information needed to deliver the image, including your IP address. We suppress the page referrer on these image requests; calculator inputs and worksheet values are not sent with them.

Messages you send us

The contact form sends your report, your reply address, your name if you give one, and any page or source you add through Cloudflare, which runs an automatic security check that never asks you to solve anything.

We keep each report in our contact inbox at Cloudflare for 12 months, then it is deleted automatically, and a copy goes to a private Discord channel our team reads. We use your reply address only to answer you, never for marketing. To see or delete a report you sent, ask through the same form and we will delete both copies.

Cloudflare Turnstile receives browser and connection information while checking for automated submissions. Please do not include passwords, payment details or other sensitive personal information in a report.

Your project notes and row count

The row counter saves a completed count in this browser. Its Erase saved count button removes that number. Private browsing or clearing browser storage may remove it too.

The planning tools and printable project worksheet use your entries locally. Project measurements and worksheet notes are not submitted to us. Printing or saving a PDF uses your browser.