YardageMath
Menu

How We Calculate

Every number our calculators show comes from the sources below. Values are checked against the sources listed. Materials vary, so every value is editable in the calculator. Confirm final quantities with your supplier.

Last updated:

Core formulas

All volume tools share the same geometry, done in feet and converted at the end:

  • Volume (cu ft) = area (sq ft) × depth (ft)
  • Cubic yards = cubic feet ÷ 27 (a cubic yard is 3 × 3 × 3 ft)
  • Cubic meters = cubic yards × 0.764555
  • Tons = cubic yards × material density
  • Bags = volume (cu ft) ÷ bag size, rounded up
  • Feet + inches → decimal feet = feet + inches ÷ 12

Material densities (tons per cubic yard)

Nominal dry, loose values aggregated from landscape-supply yards and USDA/engineering references. Bulk density changes with moisture and material — confirm tonnage with your supplier. Checked October 8, 2026.

MaterialTons / cu yd
Gravel1.4
Crushed stone1.4
Sand1.35
Topsoil1.1
Mulch0.3
Concrete (wet)2
River rock1.35
Decomposed granite1.3
Compost0.6
Riprap1.5

Sources: Inch Calculator; Inch Calculator; Cubic Yard Estimator — accessed October 8, 2026.

Bag sizes (cubic feet per bag)

MaterialCu ft / bag
Mulch2
Gravel / sand0.5
Soil (40 lb)0.75
Soil (large)1
Compost1

Concrete bag yields

Mixed-concrete yield per bag, per the manufacturer data sheet (Quikrete). Checked October 8, 2026.

BagCu ft yieldBags per cu yd
80 lb0.645
60 lb0.4560
40 lb0.390

Sources: QUIKRETE — accessed October 8, 2026.

Concrete block (CMU)

  • Blocks per sq ft = 144 ÷ (8 × 16) = 1.125 (112.5 per 100 sq ft)
  • Mortar ≈ 13 standard blocks per 80 lb bag (Quikrete Mortar Mix data sheet)
  • Core-fill grout per sq ft of wall (NCMA TEK): 6″ = 0.17, 8″ = 0.26, 12″ = 0.42 cu ft

Sources: NCMA / Concrete Masonry & Hardscapes Association; QUIKRETE — accessed October 8, 2026.

Acres per hour & field efficiency

Acres per hour = (width in inches × mph × efficiency) ÷ 99 (equivalently width ft × mph × efficiency ÷ 8.25). The constant converts 5,280 ft/mile and 43,560 sq ft/acre. Efficiency presets follow ASABE field-efficiency ranges:

EquipmentEfficiency
Zero-turn mower (80–85%)82%
Push mower (70–80%)75%
Tractor + implement (70–85%)78%

Sources: ASABE (ANSI preview); Iowa State University Extension — accessed October 8, 2026.

Gutter slope

Drop (in) = (run length ÷ 10) × slope per 10 ft. Presets follow manufacturer install guides:

PresetInches per 10 ft
¼" per 10 ft (minimum)0.25
½" per 10 ft0.5
¼" per foot (fast drainage)2.5

Sources: PNNL Building America Solution Center; Englert — accessed October 8, 2026.

Riprap stone classes

Representative gradations and layer thicknesses, per FHWA HEC-11 and NCHRP 568; your state DOT tables govern.

ClassD50 sizeLayer thickness
Light / Class I4–6 in12"
Medium / Class II9–12 in18"
Heavy / Class III15–18 in27"

Sources: US Federal Highway Administration; Transportation Research Board — accessed October 8, 2026.

Rounding & waste

Results are rounded for display (usually to two decimals); counts of bags, blocks and bars are always rounded up so you don't come up short. Default waste allowances: yardage 5%, concrete slab 10%, block 5%, carpet 10%. You can change the waste percentage on every tool.

Prices

All prices are editable 2026 national-average estimates for planning, not quotes. The default ready-mix price (~$160/cu yd) and lawn-mowing tiers sit within the ranges in the 2026 cost guides below; confirm with a local supplier. See the disclaimer.

Sources: SlabCalc (2026 cost guide); LawnStarter (2026 cost guide) — accessed October 8, 2026.

References

Every figure above links to the source it was checked against. Full list: