Concrete Pad Calculator
Enter the length, width, and thickness of your pad to get cubic yards, bag count, weight, and a cost estimate in one pass.
Enter a custom thickness in inches below.
10% covers most pours. Use 15% for hand-mixed or irregular shapes.
Ready-mix typically runs $125–$180 per cubic yard delivered.
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Concrete Pad Calculator
Short answer: multiply length by width by thickness (in feet) to get cubic feet, divide by 27 for cubic yards, then add 10% waste. A 10×10 ft pad at 4 inches thick needs about 1.36 cubic yards of concrete, or roughly 82 bags of 60 lb premix.
Formula
Concrete volume for a rectangular pad comes down to three measurements and one conversion.
| Use case | Typical thickness |
|---|---|
| Stepping stones, thin overlay | 3 in |
| Patio, walkway, shed base | 4 in |
| Light vehicle apron, AC pad near driveway | 5 in |
| Driveway, garage floor | 6 in |
Worked example
Pad: 10 ft × 12 ft, 4 in thick, 10% waste.
- Cubic feet: 10 × 12 × (4 ÷ 12) = 40 ft³
- Add 10% waste: 40 × 1.10 = 44 ft³
- Cubic yards: 44 ÷ 27 = 1.63 cy
- 60 lb bags: 44 ÷ 0.45 = 98 bags
- 80 lb bags: 44 ÷ 0.6 = 74 bags
- Weight: 44 × 150 ÷ 2000 = 3.3 tons
Assumptions this calculator makes
- Concrete density of 150 lb per cubic foot, standard for normal-weight mix.
- 60 lb bags yield 0.45 cubic feet and 80 lb bags yield 0.6 cubic feet, per manufacturer coverage charts.
- Subgrade is compacted and level, with no allowance for a gravel base layer.
- Rectangular or square pad. Circular or irregular shapes need their own area calculation first.
Common mistakes
- Entering thickness in feet instead of inches, which inflates the volume by 12x.
- Skipping the waste allowance and coming up short mid-pour.
- Assuming every bag brand yields the same coverage — check the bag label, since yields vary slightly by manufacturer.
- Not compacting or wetting the subgrade before pouring, which leads to settling cracks later.
- Forgetting expansion or control joints on pads over about 10 ft in any direction.
- Ordering ready-mix below the supplier’s minimum load without checking short-load fees.
FAQ
How much concrete do I need for a 10×10 pad?
A 10 ft by 10 ft pad at 4 inches thick needs about 33.3 cubic feet, or roughly 1.23 cubic yards before waste. Add 10% waste and you land around 1.36 cubic yards, which most ready-mix suppliers round up to 1.5 yards minimum.
How many bags of concrete do I need for a pad?
Divide your total cubic feet by 0.45 for 60 lb bags or 0.6 for 80 lb bags. A 10×10 pad at 4 inches thick, with 10% waste, needs about 82 bags of 60 lb concrete or 61 bags of 80 lb concrete.
What thickness should a concrete pad be?
Most residential pads are poured 4 inches thick for patios, walkways, and shed bases. Pads carrying vehicle weight, like driveway aprons or AC condenser slabs sitting near a driveway, are usually poured 5 to 6 inches thick with reinforcement.
How much does a concrete pad cost?
Ready-mix delivered concrete typically runs $125 to $180 per cubic yard depending on region and PSI strength, plus delivery minimums. Bagged concrete from a home center runs higher per cubic yard once you account for bag count, but avoids delivery minimums on small pours.
Should I add extra concrete for waste?
Yes. A 10% waste allowance is standard for most pours to cover spillage, uneven subgrade, and minor measurement error. Hand-mixed pours or irregular shapes sometimes warrant 15%.