Credits and licences

Last updated 2026-10-11

Our own code

The tools and page layouts are written for this site. The pages make no requests to other servers.

The calculators use published constants and textbook formulas, typed into our own code (no third-party tables or libraries are copied):

Concrete densities: EN 1991-1-1 Annex A (normal-weight and reinforced concrete), PCA Design and Control of Concrete Mixtures and the PCA lightweight concrete fact sheet (lightweight concrete) — reference values the calculators let you override.
Bulk densities of gravel, sand and soils: loose densities from Caterpillar’s material density table; asphalt at 110 lb per square yard per inch (146.7 lb/ft³), the design rate in Virginia DOT memo IIM-LD-158.
Swell and shrinkage of common earth: the standard soil conversion table (bank 1.00, loose 1.25, compacted 0.90).
Retaining wall units and installation: Versa-Lok unit data and guidelines; Allan Block basic installation (base and drainage rock).
Premixed concrete bag yields: the QUIKRETE Concrete Mix (No. 1101) data sheet (40, 50, 60 and 80 lb); metric bag yields derived from the same mass per volume.
Concrete block sizes: nominal 8 × 8 × 16 in family (Angelus Block CMU basics, NCMA TEK 2-1A) and the 440 × 215 mm UK block face.
Reinforcing bar sizes and weights: ASTM A615/A615M nominal values (as tabulated by Caltrans); metric bar mass from the steel density 7,850 kg/m³; cover 3 in from ACI 318 for concrete cast against earth.
Volume, slope, pitch and the grid (borrow-pit) earthwork method: standard geometry and surveying formulas; unit conversions use the exact NIST values (1 ft = 0.3048 m, 1 lb = 0.45359237 kg).

None at present. If we add any library, font or data set, it will be listed here with its licence and a link (data/credits.json, rendered below).