How We Work

This page exists because a calculator that shows a number without saying where it came from is asking for a kind of trust it has not earned. Here is how the tools on this site are actually built.

Every estimate starts from something checkable

Where a published standard exists, we use it and we cite it. Yarn weight classes come from the standard weight system. Hook and needle sizes come from the published conversion charts. Board feet uses the trade convention that lumber is priced in. Where a figure exists only as an industry rule of thumb, such as the estimate that one cubic inch of soap mould holds about 0.4 ounces of batter, we say that it is a rule of thumb and give the reasoning.

Where a figure had to be derived, we show the derivation

Some of the numbers on this site cannot be looked up, because nobody publishes them. The clearest example is how much fabric a yard of yarn covers. That figure is derived from a project whose total yardage is well established, and the derivation is written into the source code so that anyone editing it can see the reasoning and check whether it still holds.

This matters because a derived figure that loses its explanation becomes an invented figure the moment someone changes it.

Assumptions are part of the answer

Every calculator page states its assumptions in plain language: what it assumes about waste, about gauge, about density, about what a "standard" project looks like. Where those assumptions are the difference between an estimate and a guess, the page says so, and tells you what to test yourself. Material quantities are the obvious case, which is why so many pages end with advice to make a swatch, a sample or a test piece first.

Estimates are labelled as estimates

Nothing on this site claims to be exact. A yarn estimate built from an average coverage figure and your own gauge is a good estimate and it is not a measurement. When we can tell you the honest range instead of a single figure, we do.

What we do when we get something wrong

We change it, and where the change is substantial we say so on the page. If a formula was wrong in a way that could have cost you money, tell us and we will fix it and thank you. A reader's correction is the most useful message this site receives.

What we will not publish

• Prices we made up, presented as market prices.
• Safety instructions for chemicals, kilns or machinery.
• Structured data that claims ratings, reviews or certifications the site does not have.
• AI generated text published without a person reading and editing it first.

Advertising

The site is free to use and is funded by advertising where it appears. Ads are placed so that they never cover a form field, a button or a result, and every tool works exactly the same whether advertising is switched on or off. Advertising has no influence on what a calculator computes.