Example 1 — 10×10 ft slab
- 10 × 10 × 0.33 ft
- +5% waste
- 0 deductions
1.28 yd³
How much concrete for a 10×10×0.33 ft slab at 5%? 34.65 ft³ → 1.28 yd³.
Concrete Calculator
Enter length, width, and thickness in the header unit. In feet, a 4-inch thickness is about 0.33 ft, not 4. The calculator multiplies the three sizes and the count, adds waste, and subtracts deductions. A 10×10×0.33 ft slab at 5% is 1.28 yd³. A 30×1.5×1 ft footing at 10% is 1.83 yd³. Six 1×1×4 ft posts at 5% are 0.93 yd³.
Results
Enter length, width, thickness, and the count. The result appears here.
Volume = length × width × thickness × count × (1 + waste/100), minus deductions. Related: mortar and cement in mortar. Article: how much concrete to order.
How the results are calculated
Slab10 × 10 × 0.33 ft
Waste5%
Volume1.28 yd³
The concrete calculator finds the volume to order. The formula multiplies length, width, thickness, and count, then by (1 + waste/100), and subtracts any deduction. The result does not go below zero. In feet, a 4-inch thickness is about 0.33 ft, not 4.
A 10×10×0.33 ft slab at 5% waste is 33 ft³ plus 1.65 ft³, which is 1.28 yd³. A 30×1.5×1 ft footing at 10% is 1.83 yd³. Six 1×1×4 ft posts at 5% are 0.93 yd³. Twelve 4×1×0.5 ft treads at 8% are 0.96 yd³.
Slab, footing, and posts use the same formula. Only the field labels change. Enter length, width, and thickness in the header unit. Count, deduction, waste, and price are optional. An empty count means one piece. An empty waste field means 0%.
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. Sand and gravel under a slab are on separate volume calculators.
Five percent waste on 33 ft³ is an extra 1.65 ft³. With a pump and an uneven base, some mix stays outside the form. Dry-mix bags are a different product on the mortar-bags page. Entering 4 in a foot field makes a 4 ft slab.
Enter 10, 10, and 0.33, set 5%, and match 1.28 yd³. Then 30, 1.5, and 1 at 10%: the footing is 1.83 yd³.
How to use this calculator
- Choose slab, footing, or posts. Field labels follow that choice.
- Enter length, width, and thickness in the header unit. In feet, a 4-inch thickness is about 0.33 ft, not 4.
- If you pour several identical pieces, enter how many. Six posts means 6.
- Enter 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 yd³. 30×1.5×1 ft and 10% give 1.83 yd³.
- Cement and mortar bags are on their own pages. This calculator stays on concrete volume.
Formula
V = max(0, L × W × H × count × (1 + waste/100) − deduction)
In feet, a 4-inch thickness is about 0.33 ft. A 10×10×0.33 ft slab at 5%: 10×10×0.33×1.05 = 34.65 ft³ = 1.28 yd³. A 30×1.5×1 ft footing at 10% is 1.83 yd³. This is order volume, not mix class.
yd³ of a 10×10×0.33 ft slab
Volume from three sizes, count, waste, and deduction. A 10×10×0.33 ft slab at 5% is 1.28 yd³.
- yd³
- Order unit in US feet mode. 10×10×0.33×1.05 = 34.65 ft³ = 1.28 yd³. A 30×1.5×1 ft footing at 10% is 1.83 yd³.
- waste
- Percent added before deduction. 5% on 33 ft³ is +1.65 ft³. An empty field means 0%.
- in
- In feet, about 0.33 ft for a 4-inch thickness. Six 1×1×4 ft posts at 5% are 0.93 yd³.
- trucks
- Indicative ~10 yd³ per delivery. A 6.34 yd³ driveway fits in one truck.
Usage examples
Example 2 — Strip footing
- 30 × 1.5 × 1 ft
- +10% waste
- 0 deductions
1.83 yd³
30×1.5×1 ft footing at 10% → 1.83 yd³. Without waste it is 1.67 yd³.
Example 3 — Six posts
- 1 × 1 × 4 ft
- × 6
- +5% waste
- 0 deductions
0.93 yd³
Six 1×1×4 ft posts at 5% → 0.93 yd³. One post without waste is 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 do I calculate concrete volume from length, width, and thickness?
Multiply length × width × thickness × count, then by (1 + waste/100), and subtract deductions. A 10×10×0.33 ft slab at 5% → 1.28 yd³.
How much concrete do I need for a 10×10×0.33 ft slab at 5% waste?
1.28 yd³ (34.65 ft³). Without waste the slab is 1.22 yd³. In feet, a 4-inch thickness is about 0.33, not 4.
Does this concrete calculator count bags or place a ready-mix order?
No. It reports volume in yd³ (and truck-load hints). Bagged dry-mix counts and the plant order stay with the supplier or a bags page.
Is this a cement or mortar calculator?
No. Here you get concrete volume. Cement-in-mortar and mortar bags live on separate construction cards.
Is this a free concrete calculator?
Yes. Enter the sizes, waste, and optional deduction, and you see cubic yards at once. No account required.
How is concrete volume calculated?
The calculator multiplies length × width × thickness × count, then by (1 + waste/100), and subtracts deductions. The result never goes below zero. A 10×10×0.33 ft slab at 5% is 1.28 yd³.
In what order are waste and deductions applied?
Waste first, then the deduction. At 20×1.5×1.5 ft, 5% waste, and a 2 ft³ deduction, the result is 1.68 yd³.
How do I enter a 4-inch thickness?
In feet, enter about 0.33, not 4. Entering 4 would make a 4 ft slab. A 10×10×0.33 ft slab at 5% is 1.28 yd³.
What does the count field do?
It multiplies one piece before waste. An empty field means 1. Six 1×1×4 ft posts at 5% are 0.93 yd³.
What waste should I choose?
Usually 5–10%. An empty field means 0%. A 33 ft³ slab at 5% is 34.65 ft³ (1.28 yd³). An uneven base is often nearer 10%.
What do truck loads mean?
An indicative delivery count at about 10 yd³ per truck, rounded up. A 6.34 yd³ driveway fits in one truck. Real capacity depends on the plant.
How do slab, footing, and posts differ?
Same L×W×H formula. Only the field labels change. A 30×1.5×1 ft footing at 10% is 1.83 yd³.
Does the result replace a ready-mix order?
No. It is the volume to order. Mix class, pump, and truck capacity need a separate talk with the plant.
Where do I calculate cement for this volume?
On the cement-in-mortar page or the mortar-bags page. This page stays concrete volume. Bagged dry mix is a different product from ready-mix.
Does a comma in 0.33 work?
Yes. 0.33 and 0,33 are the same thickness in feet. A 10×10×0.33 ft slab at 5% still gives 1.28 yd³.
Knowledge sources
Concrete volume is a rectangular box volume plus waste. Volume units below from NIST and the cubic yard / cubic meter definitions.
Page updated October 12, 2026.