About QuantityWise

QuantityWise publishes material quantity calculators for renovation and building work, together with the reference data they run on.

What this site is for

Estimating materials is a solved problem for anyone who does it for a living and a genuinely difficult one for everybody else. The arithmetic is not hard; knowing which arithmetic applies is. How much extra tile does a herringbone floor need compared to a straight one? Does new plasterboard change how much paint you buy? Is half a cubic metre of concrete a bag job or a lorry job?

Those questions have real answers that trade estimators use every day, and they are mostly not written down anywhere a homeowner can find them. This site puts them in a calculator, publishes the figures behind it, and shows the working so you can check it rather than trust it.

How the figures are produced

Every number on the site is in one of three categories, and we say which on the page:

• Derived — calculated from geometry, with the formula printed. Grout quantity from tile size and joint width, screw counts from stud spacing, concrete volume from the shape you are pouring. You can check these yourself, and we would like you to.
• Published — manufacturer and standards figures, such as adhesive consumption per trowel notch or the placed yield of a bag of concrete mix. Brands differ, usually by 10–20%, so we use a mid-range value and tell you to check the bag.
• Working estimates — waste factors and practical paint coverage rates. These come from merchant estimating practice and installer guidance rather than a single authority. They are rounded up on purpose: running short costs far more than over-ordering, and the two errors are not symmetrical.

Where we are uncertain, the page says so. Where a figure would be misleading — carpet waste, for instance, which depends entirely on how a room divides into the roll width — we say that a percentage is the wrong tool and explain what to do instead.

What we do not do

• Structural design. Foundations, retaining walls, lintels and anything carrying a building need an engineer. The concrete calculator gives you a volume, not a specification.
• Local regulations. Fixing centres, board specifications, fire ratings and damp-proofing requirements vary by country and by building. Your local rules always take precedence over anything here.
• Product recommendations. We do not review or rank brands, and no manufacturer, merchant or brand can pay to appear on this site, be recommended, or be ranked higher.

Corrections

These pages get better when people who fit this material for a living disagree with them. If a figure does not match your experience on site, or your supplier's data sheet contradicts one of ours, please get in touch. Corrections are noted with a date on the page they affect.

Who publishes this

QuantityWise is built and maintained by one person, working from published technical data rather than from a career on site. That is worth stating plainly, because it determines what this site is good for. The geometry is checkable and the formulas are printed. The published figures are taken from manufacturer data sheets and standards, and named where they matter. The working estimates are the weakest category and are labelled as such — they are the ones a tradesman would argue with, and we would rather have the argument than the false confidence. We are not a merchant, a manufacturer or a trade body, and nobody pays us to put a number on a page. Reach us at the address on the contact page. Every route by which this site does or could earn a penny is itemised under how we make money, including the ones we refuse.

How the site is funded

The calculators are free, there is no account to create, and nothing here is behind a paywall.

The site does not currently carry advertising. It carries no affiliate or commission links. Every revenue source, current and possible, is set out in full on the how this site makes money page.

One rule governs all of it: no commercial relationship has ever changed a figure on this site, and none ever will. That promise is only worth something because the maths is published — every calculator shows its formulas and every reference figure has a page explaining where it came from. A padded quantity would be visible to anyone who checked. If you ever think a number looks commercially convenient, check it against the working and then tell us.

Last updated 2026-10-17.