Home, Trade & Construction
Calculate concrete slab volume from length, width and thickness, with cubic yards, cubic metres, bag estimates, waste allowance, optional cost and a printable pour record.
Home, Trade & Construction
Thickness in feet = thickness inches ÷ 12. Base volume in cubic feet = length feet × width feet × thickness feet. Cubic yards = cubic feet ÷ 27. Cubic metres = cubic feet × 0.028316846592. Order volume = base volume × (1 + waste percent ÷ 100). Estimated bags = order cubic feet ÷ bag yield.
This is the method behind the answer, so the result can be checked rather than simply trusted.Visual grid
Length, area, volume and material estimates are grid problems too: measure the space, account for edges and allowances, then turn the pattern into a number you can use.
Space calculations turn a real surface, room, run or volume into cells, edges and allowances that can be quoted, ordered or checked.
CalculationTime
Thickness in feet = thickness inches ÷ 12. Base volume in cubic feet = length feet × width feet × thickness feet. Cubic yards = cubic feet ÷ 27. Cubic metres = cubic feet × 0.028316846592. Order volume = base volume × (1 + waste percent ÷ 100). Estimated bags = order cubic feet ÷ bag yield.
Use this space on the printed report for client, supplier, classroom, job-location, measurement, quote or approval notes.
Thickness in feet = thickness inches ÷ 12. Base volume in cubic feet = length feet × width feet × thickness feet. Cubic yards = cubic feet ÷ 27. Cubic metres = cubic feet × 0.028316846592. Order volume = base volume × (1 + waste percent ÷ 100). Estimated bags = order cubic feet ÷ bag yield.
For a 12 ft by 10 ft slab at 4 inches thick, thickness = 4 ÷ 12 = 0.3333 ft. Base volume = 12 × 10 × 0.3333 = 40 cu ft. Cubic yards = 40 ÷ 27 = 1.4815 cu yd. With 10% overage, order volume = 1.6296 cu yd, or about 73.33 bags at 0.6 cu ft per bag before rounding up.
Master’s Tip: do not hide overage inside the dimensions. Print the measured slab volume first, then the overage line, so the pour record shows what came from geometry and what came from job-site judgement.
Standard or basis: rectangular-prism volume with international-foot to SI conversion. This is a planning and quote-note calculator, not an engineering design, building approval, mix design or supplier guarantee.
Methodology & Accuracy
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Thickness in feet = thickness inches ÷ 12. Base volume in cubic feet = length feet × width feet × thickness feet. Cubic yards = cubic feet ÷ 27. Cubic metres = cubic feet × 0.028316846592. Order volume = base volume × (1 + waste percent ÷ 100). Estimated bags = order cubic feet ÷ bag yield.
Standard or basis: rectangular-prism volume with international-foot to SI conversion. This is a planning and quote-note calculator, not an engineering design, building approval, mix design or supplier guarantee.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master’s Tip: do not hide overage inside the dimensions. Print the measured slab volume first, then the overage line, so the pour record shows what came from geometry and what came from job-site judgement.
Multiply length by width by thickness. Convert thickness from inches to feet first, then divide cubic feet by 27 to get cubic yards.
A 12 ft by 10 ft slab at 4 inches thick is 40 cubic feet, which is 1.4815 cubic yards before waste or overage.
Most practical pour notes include some overage for grade variation, spillage, form movement or ordering safety. Keep that allowance separate from the measured volume.
Divide the order volume in cubic feet by the bag yield in cubic feet, then round up to whole bags. Always check the actual bag label.
Print slab length, width, thickness, base volume, overage, cubic yards, cubic metres, bag yield/count, optional price, formula, assumptions, date, page URL and job notes.
Concrete slab estimating is a volume problem: a flat area becomes a pour quantity once thickness is included. The calculation is simple, but separating measured volume from overage prevents costly misunderstandings.
Length times width gives the surface area. Multiplying by thickness turns that area into cubic feet, cubic yards or cubic metres for ordering and planning.
Slab thickness is often written in inches while length and width are measured in feet. Converting inches to feet before multiplying keeps the volume auditable.
Small jobs may be planned by bag yield; larger pours usually use ready-mix cubic yards. A useful printout keeps both the geometric volume and the ordering basis visible.
