Example 1 — 10×10 ft slab
- 10 × 10 × 0.33 ft
- +5% waste
- 0 deductions
1.28 yd³
10 × 10 × 0.33 × 1.05 = 34.65 ft³, which is 1.28 yd³. Without waste the slab is 1.22 yd³.
Concrete calculator
Enter length, width, and thickness in the unit shown at the top of the page. When that unit is feet, a 4-inch thickness is about 0.33 ft, not 4. The calculator multiplies the three sizes and the number of pieces, adds waste, and subtracts deductions. A 10 by 10 ft slab at 0.33 ft and 5% is 1.28 cubic yards. A 30 by 1.5 by 1 ft footing at 10% is 1.83 cubic yards. Six 1×1×4 ft posts at 5% are 0.93 cubic yards.
Also useful: mortar requirement, cement in mortar. Article: how much concrete to order.
Results
Enter length, width, thickness, and the count. The result appears here.
How the results are calculated
Slab10 × 10 × 0.33 ft
Waste5%
Volume1.28 yd³
The calculator finds the volume to order. The formula multiplies length, width, height, and the number of pieces, then multiplies by (1 plus waste), and then subtracts any deducted volume. The result does not go below zero. When you are using feet, a 4-inch thickness is about 0.33 ft, not 4.
A 10 by 10 ft slab, 0.33 ft thick, at 5% waste is 33 ft³ plus 1.65 ft³, which is 1.28 cubic yards. A 30 by 1.5 by 1 ft footing at 10% is 1.83 cubic yards. Six 1 by 1 by 4 ft posts at 5% are 0.93 cubic yards. Twelve 4 by 1 by 0.5 ft treads at 8% are 0.96 cubic yards.
A slab, a footing, and posts use the same formula. Only the field labels change. Enter length, width, and thickness in the unit shown at the top of the page. The number of pieces, a deduction, waste, and a price are optional. An empty count field means one piece. An empty waste field means 0%. If you are using meters, 10 cm is 0.1 m, not 10.
Mortar for a bed is on the mortar page, and cement in a mix is on cement in mortar. Paint is on another page, because that result is area, not volume. Sand and gravel under a slab are on separate volume calculators.
Five percent waste on 33 ft³ is an extra 1.65 ft³. The slab to order is 1.28 cubic yards, and without waste it is 1.22 cubic yards. With a pump and an uneven base, some of the mix stays outside the form. Dry-mix bags are a different product. The mortar-bags page counts those bags. Typing 4 in a foot field makes a 4 ft slab, about 12 times a 4-inch thickness.
Enter 10, 10, and 0.33, set 5%, and the result is 1.28 cubic yards. Then enter 30, 1.5, and 1 at 10%. The footing is 1.83 cubic yards.
How to use this calculator
- Choose slab, footing, or posts. The field labels follow that choice.
- Enter length, width, and thickness in the unit shown at the top of the page. When you are using feet, a 4-inch thickness is about 0.33 ft, not 4.
- If you are pouring several identical pieces, enter how many. Six posts means 6.
- Enter the waste, usually 5-10%. An empty waste field means 0%. A volume deduction is optional.
- Click Calculate. 10×10×0.33 ft and 5% give 1.28 cubic yards. 30×1.5×1 ft and 10% give 1.83 cubic yards.
- Cement in the mix is on the cement page, and mortar bags are on the mortar-bags page. This page gives the concrete volume, in cubic yards when you are using feet.
Cubic yards of a 10 by 10 ft slab
Volume is the three sizes, plus waste, minus any deduction. A 10 by 10 ft slab, 0.33 ft thick, at 5% is 1.28 cubic yards.
- yd³
- When you are using feet, concrete is ordered in cubic yards. 10 × 10 × 0.33 × 1.05 = 34.65 ft³, which is 1.28 yd³. A 30 by 1.5 by 1 ft footing at 10% is 1.83 yd³.
- in
- When you are using feet, type about 0.33 ft for a 4-inch thickness. Six 1×1×4 ft posts at 5% are 0.93 cubic yards.
Usage examples
Example 2 — Strip footing
- 30 × 1.5 × 1 ft
- +10% waste
- 0 deductions
1.83 yd³
30 × 1.5 × 1 × 1.10 = 49.5 ft³, which is 1.83 yd³. Without waste the footing is 1.67 yd³.
Example 3 — Six posts
- 1 × 1 × 4 ft
- × 6
- +5% waste
- 0 deductions
0.93 yd³
1 × 1 × 4 × 6 × 1.05 = 25.2 ft³, which is 0.93 yd³. One post without waste is 4 ft³ (0.15 yd³).
Example 4
- 4 × 1 × 0.5 ft
- × 12 treads
- +8% waste
0.96 yd³
4 × 1 × 0.5 × 12 × 1.08 = 25.92 ft³, which is 0.96 yd³.
Example 5
- 30 × 4 × 0.33 ft
- +5% waste
1.54 yd³
30 × 4 × 0.33 × 1.05 = 41.58 ft³, which is 1.54 yd³.
Example 6
- 20 × 1.5 × 1.5 ft
- +5% waste
- deduct 2 ft³
1.68 yd³
20 × 1.5 × 1.5 × 1.05 − 2 = 45.25 ft³, which is 1.68 yd³.
Example 7
- 20 × 16 × 0.5 ft
- +7% waste
6.34 yd³
20 × 16 × 0.5 × 1.07 = 171.2 ft³, which is 6.34 yd³. That volume fits in one truck of about 10 yd³.
Example 8
- 3 × 3 × 1.5 ft
- × 2
- +10% waste
1.10 yd³
3 × 3 × 1.5 × 2 × 1.10 = 29.7 ft³, which is 1.10 yd³. Without waste, it would be 1.00 yd³.
Related calculators
Frequently asked questions
How much concrete for a 10×10 ft slab, 0.33 ft thick, at 5% waste?
1.28 cubic yards. 10×10×0.33 is 33 ft³, and 5% brings it to 34.65 ft³, which is 1.28 yd³.
How much concrete for a 30×1.5×1 ft footing at 10%?
1.83 cubic yards. Without waste the footing is 1.67 yd³.
How much concrete for 6 posts 1×1×4 ft at 5%?
0.93 cubic yards. One post without waste is 4 ft³ (0.15 yd³). Six posts without waste are 24 ft³ (0.89 yd³), and 5% waste brings that to 25.2 ft³ (0.93 yd³).
How do I type a 4-inch thickness?
Enter 0.33. Four inches is one third of a foot, and 0.33 is the rounded figure these examples use. Entering 4 in a foot field would make a 4 ft slab.
How much concrete for a sidewalk 30 ft by 4 ft at 0.33 ft and 5% waste?
1.54 cubic yards. 30 × 4 × 0.33 = 39.6 ft³, and 5% waste brings it to 41.58 ft³. Enter 0.33 ft for a 4-inch thickness. That is the rounded one-third of a foot. The fields use the unit shown at the top of the page.
How much concrete for a driveway 20 × 16 ft at 6 inches and 7% waste?
6.34 cubic yards. That is the volume of this slab.
How much concrete for 12 treads 4×1×0.5 ft at 8%?
0.96 cubic yards. The count multiplies one tread, and the calculator applies waste after that.
Are deductions subtracted before waste?
No. The calculator applies waste first, then subtracts deducted volume. The result does not go below zero.
Where do I calculate the cement for this volume?
On the cement in mortar page, or on the mortar-bags page. This page reports concrete volume. When you are using feet, that volume is in cubic yards.
What waste should I add to a slab?
Usually 5 to 10 percent. A slab of 33 ft³ at 5% is 34.65 ft³, which is 1.28 yd³. An uneven base usually needs waste closer to 10%.
Does an empty count mean zero elements?
An empty count field means one piece. The calculator rejects zero and fractions, because you are counting whole pieces.
How many cubic yards for a 200 ft² patio 4 inches thick at 5%?
200 × 0.33 × 1.05 = 69.3 ft³, which is 2.57 cubic yards. That is the same kind of slab as 10 by 10 ft, only larger.
Knowledge sources
Volume and waste come from the sizes you enter. Below are a definition of volume and the NIST guide to SI units.
Page updated September 28, 2026.