How it works
Every sheet takes the measurements you type, works out the geometry, applies one published figure for the material (a density, a coverage or a bag yield), adds the waste allowance you can see, and multiplies by a price you can change. Nothing is hidden and nothing is rounded silently: the line says what it was computed on.
The geometry
Area is length × width; volume is area × depth in feet; a cubic yard is 27 cubic feet. Round shapes use π r², triangles base × height ÷ 2, and roof areas the pitch multiplier √(1 + (rise ÷ 12)²). Where a shape is an estimate by convention, such as a kidney-shaped pool at 75 % of its enclosing rectangle, the line says so.
The material figures
Densities and coverages are the usual planning figures for each material, and each one is printed on its own sheet under “where these figures come from”. They are typical values, not guarantees: gravel between 1.3 and 1.5 tons per cubic yard, topsoil 1.0 to 1.5 depending on moisture, a gallon of paint 350 to 400 square feet on a smooth primed wall. Bag yields for concrete are the manufacturer’s published figures: an 80 lb bag makes 0.60 cubic feet, a 60 lb bag 0.45. Every one of these is an editable field, so if your supplier quotes a different figure you can use theirs.
Waste
The waste or settling allowance is a visible input with a stated default: 5 % for bulk materials that settle, 7–10 % for cut goods like pavers and tile, 15 % or more for diagonal layouts and patterned wallpaper. It is never applied invisibly, and you can set it to zero.
Prices
Every price on the site is a typical US figure at the date printed on the sheet (2026-09-04), included so the total means something on the first visit. They are placeholders for the price you are quoted. Delivery, minimum-order fees, tax and labour are not included unless a line says so.
Units
The unit switch converts every field and every result, including the prices: a price per cubic yard becomes a price per cubic meter, a price per square foot becomes one per square meter. The arithmetic is done in US customary units and converted at the edges, so the two modes always agree.
What these will not do
They will not size a footing, choose a joist span, tell you the code in your town, or replace a quote. Structural, code and permit questions belong to your building department and a licensed contractor. Where a calculator touches one of those, such as the stair or deck sheet, it prints the residential code limit it is checking against and says to confirm it locally.
Corrections
If a figure disagrees with a manufacturer’s current table, send the product and the source to hello@yardmath.com and it will be checked. The pad holds 25 calculators; prices and defaults are re-checked before each spring.