Skip to content

Data Sources & Assumptions

Planning calculators need default numbers. Ours come from common trade references and supplier labels — not scraped price sites.

Material densities

| Material | US planning factor | Notes | |----------|-------------------|-------| | Compacted gravel | ~1.4 tons/yd³ | Crushed stone sub-base | | Dry sand | ~1.35 tons/yd³ | Bedding sand | | Mulch (bulk) | By volume | Sold loose or in 2 ft³ bags |

UK metric tools use tonnes per cubic metre with similar ratios.

Bag yields (concrete)

| Bag | Approximate yield | |-----|-------------------| | 60 lb (US) | 0.45 ft³ | | 80 lb (US) | 0.60 ft³ | | 25 kg (UK) | 0.0125 m³ |

Check the bag label — brands differ slightly.

Paint coverage

  • US: ~350 ft² per gallon per coat on a smooth, primed wall
  • UK: ~12 m² per litre per coat under the same conditions

Textured or porous surfaces need more. The Paint Calculator does not auto-add a texture factor.

Default prices

Cost fields use round national planning figures (ready-mix per yd³, gravel per ton, paint per gallon, and so on). Override them with your supplier quote — that is the intended workflow.

What we do not use

  • Live API price feeds (would imply false precision)
  • Copied tables from other websites
  • AI-generated market averages without a stated basis

Corrections

If a default is wrong for your region, override it in the tool. If you think our built-in default should change site-wide, contact us with a source (supplier price sheet, product label, or code reference).