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Nest Quantum

Methodology

Constants last checked against their sources on September 7, 2026.

Last reviewed September 7, 2026 by the developer who builds and maintains this site. Rewritten as the index of the sixty published workings. It had restated about twenty constants by hand, one of them a utility rate no calculator on the site has ever used.

What this page is

Every calculator on this site publishes its own working. Open any one of them and, underneath the results, you will find the arithmetic in notation, each variable named, a worked example, and every constant the formula uses: its value, what population it applies to, which document it came from and when that document was read, or the derivation where nothing published it.

This page is the index of those 53 blocks. It does not repeat the figures, because a second copy of a number is a number that can drift from the first. It says how the figures are chosen, what the labels on them mean, which documents this site relies on, and what it deliberately does not do.

Across 60 calculators there are 181 constants on record, and 14 of them cite a published document. That is a small proportion and it is worth saying why. Most of what these calculators supply is not the kind of thing a body publishes: 143 constants are modelled, derived from something else and shown with the arithmetic that produced them; 19 are settled figures that no single organisation publishes, like the size of a standard interior door; and 11 are definitional, like the number of square inches in a square foot.

Where a figure could have been taken from a published document, it was, and the document is named on the calculator that uses it. Where it could not, the derivation is shown instead of a citation to something that does not contain it. The remaining 7 calculators hold no constants at all: every number they use comes from what you type into them.

How a constant is chosen, and what its label means

A constant is a number the calculator supplies rather than one you enter: the energy in a kilowatt hour, the area a gallon of paint covers, the seasonal heat loss of an average house. Each one carries a label saying how firm it is, and separately says where it came from. Those are two different facts and this site shows them as two.

Published figure
Taken directly from the document named beside it. Nothing has been adjusted.
Published range, narrowed
A source publishes a range and the calculator uses a representative value from inside it. The range is stated so you can see where in it the value sits.
Modelled from published data
Derived rather than measured, and calibrated against the document named beside it. The arithmetic that produced the number is written out in full.
Modelled
Derived rather than measured, with nothing published to calibrate against. The arithmetic that produced the number is written out in full.
Well established
A settled figure that no single body publishes. A standard interior door is 36 by 80 inches; that is not in dispute and it is not in a standards document either, so the derivation is shown rather than a citation invented for it.
Definitional
True by definition. There are 144 square inches in a square foot because a foot is twelve inches. Nothing to cite, and the arithmetic is shown.

Where a figure has no source, the record says so plainly rather than citing a document that does not contain it. A citation to something that does not say the thing is worse than no citation, because it looks like evidence.

Every source this site cites

11 documents, from 6 publishers. Each has been read; nothing is listed on the strength of a search result summary or a remembered figure. The date each was published and the month it was last read are shown on the calculator that uses it.

When the figures were last checked

Every constant on this site was checked against its source on September 7, 2026. Each calculator states its own review date at the top of its published working, and that date is the date the check happened rather than the date the page was last touched.

A constant is checked again whenever any of the following happens:

  • The document it came from is revised, or withdrawn.
  • Someone reports a figure that does not match what they measured.
  • A cost figure passes twelve months, because material and labour prices move faster than physical constants do.
  • The formula that uses it changes for any reason.

Corrections

If a number here is wrong, we want to know, and the fastest way to find out is for someone to check it. Every published working ends with a link to report a figure that looks wrong. Tell us what you found and what you expected, and we will check it against the source.

Where a correction changes an answer, it is made in the code, the constant's record is updated with the new source, and the change is published rather than quietly deployed. Every one of them is on the corrections page, with what the site said before and what it says now. The editorial policy sets out how that works.

Waste and contingency

Every material calculator includes a waste factor and every cost calculator a contingency. They are not padding. Material waste accounts for cuts, breakage, irregular shapes, overspray and ordering minimums; cost contingency accounts for scope changes, discovered conditions and price movement between estimating and buying.

The default is set for someone doing the work themselves for the first time. A professional working from a measured drawing will usually need less, and the factor is adjustable on every calculator that has one. Where a waste factor is applied, it is applied to the continuous quantity and rounded up once at the end, so the figure you are given is the figure to order.

What this site does not do

These are planning estimates. They are useful for deciding what to buy and roughly what it will cost, and they are not a substitute for a measurement, a quote or a professional opinion. Specifically:

  • They do not know your local prices. Material and labour costs vary substantially between markets, and a national average is the wrong number for any particular job by some amount we cannot tell you.
  • They do not know your surface. Coverage rates depend on porosity, texture and what is already on the wall. The figure on the container is the authority.
  • They do not know your building. Structural work, electrical, plumbing, HVAC and anything requiring a permit is governed by local code and by an inspector, not by a calculator.
  • They do not replace a written quote. A contractor's number is binding and ours is not.

Where a comparison comes out unfavourable, these calculators say so. A payback period that never arrives is reported as never, not left blank, and a saving that is smaller than the cost is shown as a loss.

The published workings

Every calculator, each with its own constants, sources and derivations underneath the results.

Written and maintained by the developer who builds and maintains this site. One person is answerable for every figure on this site, which is the point of publishing where each of them came from. Corrections go to [email protected] and get a reply within two working days.