How many cubic yards of concrete is my slab?

Length times width times thickness, converted into cubic yards, which is what the large figure on this page is. A slab 12 feet by 10 feet by 5 inches is 50 cubic feet, and a cubic yard is 27 cubic feet, so it is 1.85 cubic yards before waste and 2.04 with a 10 percent allowance. Type your own measurements and the figure follows; the thickness field takes inches or millimetres directly, so nothing needs converting first.

How much area does one cubic yard of concrete cover?

Choose Coverage from volume, enter 1 cubic yard, set waste to 0 percent and enter your specified thickness. One cubic yard is 27 cubic feet: it covers 81 square feet at 4 inches, 64.8 at 5 inches or 54 at 6 inches. A 10 percent allowance leaves 73.64 square feet at 4 inches, because usable geometry is 1 ÷ 1.10 cubic yards. As dimension checks, 9 feet by 9 feet by 4 inches, 8 feet by 8.1 feet by 5 inches and 9 feet by 6 feet by 6 inches all read 1.00 cubic yards before waste, whatever allowance is set.

Why does a part yard get ordered as a whole one?

Suppliers choose their ordering increments, minimum loads and delivery charges. This page reports a calculated volume with a rounded display; it does not round the order to a truck quantity. Confirm the increment and total delivered price with your supplier.

How much extra should I order?

Enter the allowance specified for your job from 0 to 100 percent. The 0%, 5% and 10% buttons are shortcuts. In dimension or known-volume mode, total = geometric volume × (1 + allowance ÷ 100). In coverage mode, usable geometry = available supply ÷ (1 + allowance ÷ 100). The page cannot infer site loss from the measurements.

You can read both volume and bag count. A 10 by 20 foot pad at a supplied 4 inch thickness with 10 percent waste is 2.72 cubic yards, needing 123 example 80 lb bags at 0.60 cubic feet per bag. Bag yields vary, so enter the mixed-concrete yield printed on your product. Compare delivery and mixing arrangements with your supplier.

Can it tell me how thick the slab needs to be?

No. Thickness is something you type in and this page reports back inside the volume, never something it produces. A thickness chosen for a load is structural, so it belongs with an engineer or your local code, not with a volume calculator. Nothing here prints a thickness, a rebar size or a mix strength.

How many 80 lb, 60 lb or 40 lb bags are in a cubic yard?

At the approximate example yields of 0.60, 0.45 and 0.30 cubic feet per bag, one cubic yard (27 cubic feet) needs 45, 60 or 90 bags before waste. Volume to bags calculates a count from any entered volume. Bags to volume reverses it: 45 bags at 0.60 cubic feet yield one cubic yard. Custom accepts the product-specific printed yield. These are volume-yield calculations, not a universal conversion from dry bag weight.

Are square yards and cubic yards the same for concrete?

Square yards measure area; cubic yards measure volume. The footprint readout provides area, and multiplying by your supplied thickness produces concrete volume. Coverage from volume works in reverse and reports square feet, square yards and square meters. It never derives a structural thickness. Area to volume accepts a measured area directly in square feet, square yards or square meters.

Can I enter a circular slab or check a cubic-yard formula?

Yes. Select Circle in Slab dimensions and enter diameter and supplied thickness. Volume is π × (diameter ÷ 2)² × thickness; a triangle uses base × perpendicular height × thickness ÷ 2. For a rectangle measured in feet with thickness in inches, cubic yards before waste = length × width × thickness ÷ 324. The working is displayed with the supplied measurements.

Concrete Yard Calculator

Calculate cubic yards from measured slab dimensions, or switch to Area to volume, Volume to bags, Bags to volume or Coverage from volume. The yard preset leads with cubic yards for volume and square feet for coverage. Select a rectangle, circle or triangle and mix imperial and metric dimensions freely. A supplied allowance increases the volume needed; in coverage mode the same allowance reduces the area your available supply covers. Approximate bag presets can be replaced with the mixed-concrete yield printed on your bag.

Volume with allowance10% allowance

Cubic yards2.04yd³1.56 m³ · 55.00 ft³ · 1.85 yd³ before waste

80 lb example bags92

Mix dimension units freely. Bag presets use approximate yields of 0.30, 0.45 and 0.60 ft³; choose Custom to use the mixed-concrete yield printed on your bag. Counts round up to whole bags.

How this is calculated

length × width × supplied thickness. 12 ft long × 10 ft wide × 5 in thick.

Slab footprint: 120.00 ft² · 11.15 m² · 13.33 yd².

Volume with allowance: 2.04 yd³ · 1.56 m³ · 55.00 ft³. Bag count = volume ÷ yield, rounded up: 92 at 16.9901 litres per bag.

12 ft x 10 ft x 5 inone-car pad, 10% waste
2.04 yd³ · 1.56 m³ · 92 bags
20 ft x 20 ft x 0.5 ftdouble garage, all in feet, no waste
7.41 yd³ · 5.66 m³ · 334 bags
3 m x 3 m x 100 mmmetric entry, 5% waste
1.24 yd³ · 0.95 m³ · 56 bags

Measured concrete geometry. Geometry uses exact unit definitions with browser-number arithmetic and rounded displays. Bag yields are approximate; use the yield on your bag. Thickness and waste are supplied inputs, not structural recommendations. This page does not calculate load capacity, reinforcement, mix design, supplier prices or installation costs. For varying-depth, thickened-edge, footing or monolithic work, this flat-slab model does not total those extra sections.

Common questions

How many cubic yards of concrete is my slab?: Length times width times thickness, converted into cubic yards, which is what the large figure on this page is. A slab 12 feet by 10 feet by 5 inches is 50 cubic feet, and a cubic yard is 27 cubic feet, so it is 1.85 cubic yards before waste and 2.04 with a 10 percent allowance. Type your own measurements and the figure follows; the thickness field takes inches or millimetres directly, so nothing needs converting first.
How much area does one cubic yard of concrete cover?: Choose Coverage from volume, enter 1 cubic yard, set waste to 0 percent and enter your specified thickness. One cubic yard is 27 cubic feet: it covers 81 square feet at 4 inches, 64.8 at 5 inches or 54 at 6 inches. A 10 percent allowance leaves 73.64 square feet at 4 inches, because usable geometry is 1 ÷ 1.10 cubic yards. As dimension checks, 9 feet by 9 feet by 4 inches, 8 feet by 8.1 feet by 5 inches and 9 feet by 6 feet by 6 inches all read 1.00 cubic yards before waste, whatever allowance is set.
Why does a part yard get ordered as a whole one?: Suppliers choose their ordering increments, minimum loads and delivery charges. This page reports a calculated volume with a rounded display; it does not round the order to a truck quantity. Confirm the increment and total delivered price with your supplier.
How much extra should I order?: Enter the allowance specified for your job from 0 to 100 percent. The 0%, 5% and 10% buttons are shortcuts. In dimension or known-volume mode, total = geometric volume × (1 + allowance ÷ 100). In coverage mode, usable geometry = available supply ÷ (1 + allowance ÷ 100). The page cannot infer site loss from the measurements.
Bags or ready-mix?: You can read both volume and bag count. A 10 by 20 foot pad at a supplied 4 inch thickness with 10 percent waste is 2.72 cubic yards, needing 123 example 80 lb bags at 0.60 cubic feet per bag. Bag yields vary, so enter the mixed-concrete yield printed on your product. Compare delivery and mixing arrangements with your supplier.
Can it tell me how thick the slab needs to be?: No. Thickness is something you type in and this page reports back inside the volume, never something it produces. A thickness chosen for a load is structural, so it belongs with an engineer or your local code, not with a volume calculator. Nothing here prints a thickness, a rebar size or a mix strength.
How many 80 lb, 60 lb or 40 lb bags are in a cubic yard?: At the approximate example yields of 0.60, 0.45 and 0.30 cubic feet per bag, one cubic yard (27 cubic feet) needs 45, 60 or 90 bags before waste. Volume to bags calculates a count from any entered volume. Bags to volume reverses it: 45 bags at 0.60 cubic feet yield one cubic yard. Custom accepts the product-specific printed yield. These are volume-yield calculations, not a universal conversion from dry bag weight.
Are square yards and cubic yards the same for concrete?: Square yards measure area; cubic yards measure volume. The footprint readout provides area, and multiplying by your supplied thickness produces concrete volume. Coverage from volume works in reverse and reports square feet, square yards and square meters. It never derives a structural thickness. Area to volume accepts a measured area directly in square feet, square yards or square meters.
Can I enter a circular slab or check a cubic-yard formula?: Yes. Select Circle in Slab dimensions and enter diameter and supplied thickness. Volume is π × (diameter ÷ 2)² × thickness; a triangle uses base × perpendicular height × thickness ÷ 2. For a rectangle measured in feet with thickness in inches, cubic yards before waste = length × width × thickness ÷ 324. The working is displayed with the supplied measurements.

Geometry uses exact unit definitions with browser-number arithmetic and rounded displays. Bag yields are approximate; use the yield on your bag. Thickness and waste are supplied inputs, not structural recommendations.