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Estimate concrete volume for a rectangular pour from length, width and thickness, with cubic yards, cubic metres, bag estimates, ready-mix cost, visible overage and a printable pour-planning record.
Calculator
Thickness feet = thickness inches ÷ 12. Base cubic feet = length × width × thickness feet × matching pours. Base cubic yards = base cubic feet ÷ 27. Order cubic yards = base cubic yards × (1 + overage percent ÷ 100). Cubic metres = order cubic yards × 0.764554857984. Bags needed = ceiling(order cubic feet ÷ bag yield). Optional ready-mix cost = order cubic yards × price per cubic yard.
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 feet = thickness inches ÷ 12. Base cubic feet = length × width × thickness feet × matching pours. Base cubic yards = base cubic feet ÷ 27. Order cubic yards = base cubic yards × (1 + overage percent ÷ 100). Cubic metres = order cubic yards × 0.764554857984. Bags needed = ceiling(order cubic feet ÷ bag yield). Optional ready-mix cost = order cubic yards × price per cubic yard.
Use this space on the printed report for client, supplier, classroom, job-location, measurement, quote or approval notes.
Thickness feet = thickness inches ÷ 12. Base cubic feet = length × width × thickness feet × matching pours. Base cubic yards = base cubic feet ÷ 27. Order cubic yards = base cubic yards × (1 + overage percent ÷ 100). Cubic metres = order cubic yards × 0.764554857984. Bags needed = ceiling(order cubic feet ÷ bag yield). Optional ready-mix cost = order cubic yards × price per cubic yard.
For a 12 ft × 10 ft slab at 4 in thick, thickness = 4 ÷ 12 = 0.3333 ft. Base volume = 12 × 10 × 0.3333 = 40 ft³, or 1.4815 yd³. With 10% overage, order volume is about 1.63 yd³.
Master’s Tip: print the base volume and order volume separately. A quote note that only says “1.63 yd³” is hard to audit unless the dimensions, thickness, overage and bag-yield assumptions stay attached.
Standard or basis: rectangular-prism volume takeoff using feet, inches and cubic yards, with 1 yd³ = 27 ft³ and 1 yd³ = 0.764554857984 m³. Concrete strength, reinforcement, joints, base preparation, curing and local code requirements must be checked separately.
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 feet = thickness inches ÷ 12. Base cubic feet = length × width × thickness feet × matching pours. Base cubic yards = base cubic feet ÷ 27. Order cubic yards = base cubic yards × (1 + overage percent ÷ 100). Cubic metres = order cubic yards × 0.764554857984. Bags needed = ceiling(order cubic feet ÷ bag yield). Optional ready-mix cost = order cubic yards × price per cubic yard.
Standard or basis: rectangular-prism volume takeoff using feet, inches and cubic yards, with 1 yd³ = 27 ft³ and 1 yd³ = 0.764554857984 m³. Concrete strength, reinforcement, joints, base preparation, curing and local code requirements must be checked separately.
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: print the base volume and order volume separately. A quote note that only says “1.63 yd³” is hard to audit unless the dimensions, thickness, overage and bag-yield assumptions stay attached.
Multiply length by width by thickness in feet to get cubic feet, then divide by 27 to get cubic yards. Add a visible overage allowance before ordering.
There are exactly 27 cubic feet in one cubic yard. A cubic yard is 3 ft × 3 ft × 3 ft.
A 5% to 10% allowance is often used for small planning estimates, but uneven subgrade, forms, pump lines and site conditions can change the order. Keep the allowance visible rather than hiding it in the dimensions.
Bag yield is for dry bagged concrete products. Ready-mix is normally ordered by cubic yard or cubic metre, so use the cubic-yard result and supplier guidance for truck delivery.
Print the length, width, thickness, matching sections, base cubic feet, order cubic yards, overage, bag yield, formula, page URL, date and notes for reinforcement, forms, subgrade and supplier discussion.
Concrete estimating is a volume problem, but the useful record is a pour note: dimensions, thickness, base cubic feet, order cubic yards, allowance, bag yield and supplier assumptions all belong together.
For a simple slab or pad, the arithmetic is length × width × thickness. The common mistake is leaving thickness in inches instead of converting it to feet before multiplying.
In the United States and many trade contexts, ready-mix concrete is quoted in cubic yards. Showing cubic feet, cubic yards and cubic metres makes the record easier to compare across suppliers and classroom examples.
A separate overage line is more honest than quietly inflating dimensions. It lets another person see what was measured and what was added for site uncertainty.