About MaterialSmith and How the Numbers Are Sourced

Methodology

Every calculator on this site follows the same four rules, and they are the same rules a good estimator applies by hand.

Work in one unit system at a time. Dimensions are entered in feet and inches; anything given in inches is converted before it is multiplied. Most estimating errors are unit errors.
Round up at the point of purchase. Tiles, sheets, rolls and bags are sold whole. When a material is mixed and placed one unit at a time, such as concrete in a post hole, the rounding happens per unit rather than once at the end.
Separate the net quantity from the waste allowance. Both are shown, so you can see what the geometry says and what the allowance added.
Publish the coverage rate and its source. Coverage is the figure that varies most between products. Each page names the manufacturer document behind the figure it uses and links to it.

Sources currently in use

Figure	Value used	Source
Thin-set mortar coverage, 50 lb bag	90 to 35 sq ft by trowel notch	Custom Building Products, VersaBond Professional Thin-Set Mortar (TDS-119)
Sanded grout density	105 lb per cu ft, 25 lb bags	Custom Building Products, Polyblend Plus Sanded Grout (TDS-360)
Gypsum panel sizes	4 ft x 8, 10 and 12 ft	USG, Sheetrock Brand Gypsum Panels product page
Joint compound, tape and fasteners	0.01 gal, 0.4 ft and about 1 screw per sq ft	Lowe's Drywall Materials Estimator
Concrete bag yields	0.6 cu ft per 80 lb, 0.45 cu ft per 60 lb	QUIKRETE, Concrete Mix product line (bag yields)
Shingle bundles and coverage per square	3 bundles, 98.4 sq ft per square	Owens Corning, TruDefinition Duration Shingles product page (bundles and coverage per square)
Mulch depth in beds	2 to 3 in for bark and wood mulch	Clemson Cooperative Extension, Home & Garden Information Center, Mulch (HGIC 1604)
Gravel density	1.4 tons per cu yd, editable on the page	Quarry-specific, no universal published figure

Coverage rates are product-specific. A rapid-setting mortar, a lightweight panel or a high-strength concrete mix will not match the figures above. Where your bag disagrees with this site, the bag wins.

Two pages deliberately publish no coverage rate at all. Mulch and gravel volumes are pure geometry: a cubic yard is 27 cubic feet by definition, so there is nothing product-specific to cite and nothing that can go out of date. The one figure that does vary for gravel, the density used to convert cubic yards to tons, depends on the quarry rather than on any standard, so it is an editable field on the page instead of a published claim.

What this site does not do

It does not collect personal information. There is no form, no account and no newsletter.
It does not set cookies. Visit counts are collected in aggregate, without identifying you.
It does not sell your details to contractors or lead brokers.
It does not follow you across other websites or profile you for advertising.
It does not replace a licensed contractor, an engineer or your local building department.

Some outbound links to suppliers earn a commission if you buy through them. That is disclosed on every page where such a link appears, and it does not change the quantity the calculator returns.

Found a number that looks wrong?

Estimating figures move: manufacturers reformulate products and revise their data sheets. If a coverage rate here no longer matches the current technical data sheet, or a formula does not handle a case you run into on site, that is worth fixing. Each page carries the date it was last reviewed, and the sources are linked so you can check them yourself rather than take our word for it.

Who publishes this site

MaterialSmith is published from France. Postal address of the publisher:

MaterialSmith
69 Rue du Rouet
13008 Marseille
France

This address is the publisher's registered contact address. It is not a showroom, a supplier or a contractor, and no material is sold or shipped from it.