Concrete Pad Calculator

Area

• Rectangle: A = L x W
• Circle: A = pi x (D/2)^2
• Custom: A = entered area

Volume

• Net volume: V = A x T
• Waste: Vw = V x (1 + waste/100)
• Unit conversion: yd3 = m3 x 1.30795

Bags and loads

• Bag count: bags = ceil(Vw / yield_per_bag)
• Loads: loads = ceil(yd3_waste / truck_capacity)

1. Select a shape and choose your measurement units.
2. Enter dimensions or a custom area, then add thickness.
3. Set a waste factor to cover jobsite variation.
4. Add pricing per cubic unit and optional area rates.
5. Press Calculate to view volume, bags, loads, and cost.
6. Use CSV or PDF buttons to export the latest results.

1) Why pad volume accuracy matters

Concrete is bought by volume, yet pads are measured by length, width, and thickness. A small thickness error can change ordering significantly. For example, adding one inch across a 12 ft x 10 ft pad increases volume by about 0.31 yd3, which can affect cost and delivery planning.

2) Choosing a practical thickness range

Common residential pads are 4 to 6 inches thick, while heavier loads often require engineered sections. Thickness selection depends on soil bearing, expected loads, and reinforcement. The calculator lets you enter thickness in inches, millimeters, or meters, then converts results consistently for ordering.

3) Waste factors and jobsite realities

Waste is not just spillage. Uneven subgrade, over-excavation, form bulge, and slope corrections add volume. A typical waste allowance is 5% to 10% for well-formed pads, and up to 15% for irregular edges. This tool applies waste directly to net volume.

4) Unit conversions you can trust

Suppliers may quote in cubic yards while drawings may be metric. The calculator computes in cubic meters, then converts using 1 m3 = 1.30795 yd3. It also reports pad area in m2 and ft2 so finish rates and reinforcement allowances can be compared across unit systems.

5) Estimating bags for small pours

Bagged mixes work best for small pads, repairs, and tight-access areas. Typical yields are roughly 0.60 ft3 for an 80 lb bag and 0.45 ft3 for a 60 lb bag, but brands differ. Use the custom yield input if your packaging lists a specific volume per bag.

6) Ready-mix loads and delivery checks

Truck capacity varies by region and access, commonly around 6 to 10 yd3. The load estimate in this calculator divides your waste-adjusted yardage by truck capacity and rounds up. It helps anticipate partial loads, short-load fees, and whether staging space is needed.

7) Cost planning with clear line items

Material cost is computed from your selected unit price per cubic meter or cubic yard. Optional finish and reinforcement rates are applied per area unit, using ft2 for imperial inputs and m2 for metric inputs. This separation supports budgeting and comparing supplier quotes consistently.

8) Using mass estimates for handling decisions

Concrete density is often near 2400 kg/m3 for normal-weight mixes. Multiplying density by waste-adjusted volume estimates total mass in kg and lb. This is useful for checking base requirements, load paths, and whether equipment access is appropriate for placement and finishing operations.

1) Should I use net volume or volume with waste?
Use volume with waste for ordering. Net volume is the geometric minimum; waste covers overfill, uneven subgrade, form leakage, and placement loss. A 5% to 10% allowance is common.

2) Which thickness should I enter for a sloped pad?
Use the average thickness. If the pad varies from 3 in to 5 in, enter 4 in. For large slopes or critical work, calculate in sections and sum volumes.

3) Why do bag counts seem high for larger pads?
Bagged concrete yields are small per bag, so counts rise quickly as volume increases. Once you approach one or two cubic yards, ready-mix is often more practical and faster.

4) How do I match supplier pricing units?
If your supplier quotes per cubic yard, fill in the yard price. For metric quotes, fill in the cubic meter price. The calculator chooses the cost basis that fits your length-unit selection.

5) What truck capacity should I use?
Use your supplier’s stated capacity, or a planning value like 9 yd3. Access constraints may reduce usable capacity. Always confirm minimum order policies and short-load fees with the dispatcher.

6) Do reinforcement costs include chairs and tie wire?
The reinforcement rate is a simple allowance per area. Include mesh or rebar, chairs, wire, and labor in that rate if you want a single line item. Otherwise keep it at zero.

7) Can I export results for my estimate file?
Yes. After you calculate, use the CSV and PDF buttons. They export the latest computed summary, which is handy for quotes, purchase orders, and field planning.