Editor
Pablo Ruiz Quintero
Every page on this site carries a byline because someone has to be answerable for the numbers. On this one, that is me.
Last reviewed 2026-09-16
What I decide
Which documents count as a source and which do not. What the default values are — the slab thickness a patio gets when you do not type one, the waste allowance for a diagonal tile layout, the point at which bags stop making sense and a truck starts. Whether a wrong figure is a correction or a routine update. And the rule that the language model on this site is never allowed to produce a number.
Those are judgements, and judgements should have a name attached. Where I have made one, the reasoning is printed beside the figure rather than buried in a methodology page nobody reads — though the methodology page is there too, and it is the honest place to start if you want to know whether to trust any of this.
Where the authority is meant to come from
Not from me. It is meant to come from the 109 documents this site reads, each named, dated and listed on the sources page with the figure it produced. If a number here is right, it is right because the data sheet says so and you can go and check the data sheet — not because of who typed it in.
That is also the test I would apply to any other calculator site, including the ones we compete with. Ask where a figure came from. If the answer is a confident tone of voice, it is not an answer.
Background
I build tools that turn a messy real-world question into a number someone can act on, and I care more about the number being defensible than about the tool being clever. This site came out of reading the whole market of construction calculators and finding the same three failures everywhere: quantities that stop at an abstract volume nobody can buy, a waste allowance hidden inside a flat ten per cent, and a regional price factor applied to materials that do not vary regionally.
How to hold me to it
Find a number you think is wrong and say so. If it is wrong it goes in corrections — the page, the old figure, the new one, how it was found and how far off it was. If it turns out to be right, the source is on the sources page and you can judge it yourself.
Send this to whoever is paying
The link carries your measurements, so whoever opens it sees the same numbers you are looking at — and you can come back to it yourself tomorrow with the delivery note in front of you.
Plain links, no tracking scripts. Nothing here reports back that you shared it.