How do I calculate a concrete pad?

Measure the pad length, width, and thickness, then multiply them to get volume. Convert cubic feet to cubic yards by dividing by 27, or let the calculator handle the conversion automatically.

How much concrete do I need for a 10x10 pad?

A 10x10 pad at 4 inches thick needs about 1.23 cubic yards before extra waste is added. With a 10% waste allowance, the order-ready total is about 1.36 cubic yards.

How many bags of concrete do I need for a 4x4 AC pad?

Using the same 0.6 cubic foot yield per 80-lb bag used in this calculator, a 4x4 pad at 4 inches thick needs about 9 bags before extra waste or about 10 bags with a 10% allowance.

How thick should a concrete pad be?

Many AC pads start around 4 inches, shed pads often land around 4 to 5 inches, and heavier equipment pads often push into the 5 to 6 inch range. Final thickness should still follow load, reinforcement, soil, and local requirements.

How much does a concrete pad cost?

This page helps estimate concrete quantity first, but the final project cost can change based on excavation, base prep, reinforcement, labor, delivery, and finishing.

Should I use the slab calculator or the pad calculator?

Use the pad calculator when the job is a small rectangular pad such as a shed base, AC pad, or equipment pad. Use the slab calculator when the project is a broader patio, walkway, or driveway slab.

Concrete Pad Calculator

Estimate cubic yards, total weight, and 40/60/80-lb bag counts for shed pads, AC pads, and equipment pads in one pad-first workflow.

Editing Section 1

Update dimensions. Results update only after Calculate.

Edited

Length

Width

Thickness

Quantity

Waste Control

Suggested 10 percent, adjust as needed.

10%

Preview

1/1 Free DailyWireframeAI Style

Results Card

Results update when you press Calculate.

Press Calculate to see results.

Calculation Details

Why this pad calculator is more useful than a generic slab entry

The pad search cluster is narrower than broad slab intent. People usually want to know how much concrete a shed pad needs, how many bags a 4×4 AC pad takes, how thick a pad should start, and whether a small pad still makes sense with bagged mix. This page keeps those answers next to the calculator instead of burying them in a wider slab workflow.

Stay pad-first from the first input

The route opens directly in a fixed rectangular pad workflow, so the page does not dilute intent with unrelated shapes.

Use small-pad size references before buying

Quick checks for 4×4, 6×8, and 10×10 pads help you pressure-test the estimate before you commit to a store run or material pickup.

Acknowledge thickness and cost questions honestly

The page covers pad thickness starting points and cost intent, but keeps the answer grounded in material planning instead of pretending to be a full installed-price quote.

Know when you really need the slab page instead

If the job is a broader patio, walkway, or driveway slab, the slab calculator is the better route because its content is built for that larger flat-pour workflow.

Reference Tables

Common Pad Sizes, Thickness Starting Points, and Bag Checks

Use these tables as quick planning references for common small-pad sizes, starting thickness ranges, and bag-yield assumptions. Final dimensions still belong to the actual jobsite and expected load.

Common small concrete pad sizes

These rows use the same rectangular volume math as the live calculator and focus on the three use cases approved for this page.

Use case

4×4 AC pad

Dimensions: 4 ft × 4 ft × 4 in
Base volume: 0.20 yd³
80-lb bags: Approx. 9 bags

Use case

6×8 equipment pad

Dimensions: 6 ft × 8 ft × 5 in
Base volume: 0.74 yd³
80-lb bags: Approx. 34 bags

Use case

10×10 shed pad

Dimensions: 10 ft × 10 ft × 4 in
Base volume: 1.23 yd³
80-lb bags: Approx. 56 bags

Use case	Dimensions	Base volume	80-lb bags
4×4 AC pad	4 ft × 4 ft × 4 in	0.20 yd³	Approx. 9 bags
6×8 equipment pad	6 ft × 8 ft × 5 in	0.74 yd³	Approx. 34 bags
10×10 shed pad	10 ft × 10 ft × 4 in	1.23 yd³	Approx. 56 bags

Bag counts are rounded and shown before extra waste. Use the calculator when pad thickness, edge thickening, or quantity changes.

Concrete pad thickness starting points

These are planning references, not code values. Final pad thickness depends on load, base prep, reinforcement, soil, and the equipment or structure above the pad.

Use case

AC condenser pad

Often starts around: 4 in
Why it changes: Small HVAC pads often stay near the basic 4-inch range when the base is stable and the unit load is known.

Use case

Shed pad

Often starts around: 4 to 5 in
Why it changes: Sheds can concentrate load through walls or anchor points, so thickness and base prep matter sooner than the square footage suggests.

Use case

Equipment / generator pad

Often starts around: 5 to 6 in
Why it changes: Heavier or vibrating equipment often pushes the pad thicker and makes reinforcement or anchorage details more important.

Use case	Often starts around	Why it changes
AC condenser pad	4 in	Small HVAC pads often stay near the basic 4-inch range when the base is stable and the unit load is known.
Shed pad	4 to 5 in	Sheds can concentrate load through walls or anchor points, so thickness and base prep matter sooner than the square footage suggests.
Equipment / generator pad	5 to 6 in	Heavier or vibrating equipment often pushes the pad thicker and makes reinforcement or anchorage details more important.

Use local code and equipment specs when the pad supports a structure, anchorage, or heavier mechanical load.

Approximate bag counts from this calculator's default yields

These counts follow the same live assumptions used across the site: 40-lb = 0.30 ft³, 60-lb = 0.45 ft³, and 80-lb = 0.60 ft³ of concrete per bag.

Bag size

40 lb

Bags per 1/2 yd³: 45 bags
Bags per 1 yd³: 90 bags
Planning note: Handling count rises quickly once the pad gets beyond a very small utility size.

Bag size

60 lb

Bags per 1/2 yd³: 30 bags
Bags per 1 yd³: 60 bags
Planning note: Useful when a supplier stocks 60-lb mix, but the labor still scales fast on larger pads.

Bag size

80 lb

Bags per 1/2 yd³: 23 bags
Bags per 1 yd³: 45 bags
Planning note: Best single reference point because the page treats 80-lb bags as the standard comparison size.

Bag size	Bags per 1/2 yd³	Bags per 1 yd³	Planning note
40 lb	45 bags	90 bags	Handling count rises quickly once the pad gets beyond a very small utility size.
60 lb	30 bags	60 bags	Useful when a supplier stocks 60-lb mix, but the labor still scales fast on larger pads.
80 lb	23 bags	45 bags	Best single reference point because the page treats 80-lb bags as the standard comparison size.

Rounded to whole bags. Add waste after the base quantity is known.

Need a broader patio, walkway, or driveway workflow instead? Switch to the slab calculator. If the job is really an isolated support footing, use the footing calculator. For round piers and sonotubes, use the column calculator.

Worked Examples

Query-backed pad examples for common small-pad planning

These examples mirror the approved pad use cases and use the same 10% waste allowance shown in the calculator workflow.

Example 1

10×10 shed pad at 4 inches

This is the clearest small-structure baseline and shows how fast a simple shed pad moves from square footage to yardage and bags.

Base volume

1.23 yd³

With 10% waste

1.36 yd³

80-lb bags

Approx. 62 bags

Use case

Shed pad

1Area = 10 × 10 = 100 sq ft.
2Thickness = 4 inches = 0.333 ft.
3Base volume = 100 × 0.333 = 33.33 ft³ = 1.23 yd³.
4Add 10% waste to land at about 1.36 yd³, or roughly 62 80-lb bags.

Takeaway: A 10×10 pad is still realistic to plan clearly, but the bag count is high enough that labor and staging deserve attention before material day.

Example 2

4×4 AC pad at 4 inches

This is a true small-pad example that fits the AC intent directly and gives a realistic bag count for a compact utility pour.

Base volume

0.20 yd³

With 10% waste

0.22 yd³

80-lb bags

Approx. 10 bags

Use case

AC pad

1Area = 4 × 4 = 16 sq ft.
2Thickness = 4 inches = 0.333 ft.
3Base volume = 16 × 0.333 = 5.33 ft³ = 0.20 yd³.
4Add 10% waste to land at about 0.22 yd³, or roughly 10 80-lb bags.

Takeaway: This is the kind of job where bagged concrete still feels practical, but the calculator keeps the count honest before the first store run.

Example 3

6×8 equipment pad at 5 inches

This example reflects the heavier small-pad case where thickness matters more and the order climbs faster than the footprint suggests.

Base volume

0.74 yd³

With 10% waste

0.81 yd³

80-lb bags

Approx. 37 bags

Use case

Equipment pad

1Area = 6 × 8 = 48 sq ft.
2Thickness = 5 inches = 0.417 ft.
3Base volume = 48 × 0.417 = 20.00 ft³ = 0.74 yd³.
4Add 10% waste to land at about 0.81 yd³, or roughly 37 80-lb bags.

Takeaway: Once thickness and equipment load rise together, a pad can leave the truly small-bag category faster than the square footage alone suggests.

Common Mistakes

Where concrete pad estimates usually go wrong

The formula is simple. Most pad mistakes come from thickness drift, confusing material cost with installed cost, or using the wrong page for the job.

Mistake 1

Treating every small pad as the same 4-inch pour

A small footprint does not automatically mean a light-duty pad. Thickness should follow the pad use case, not habit.

AC pads, shed pads, and equipment pads can start from different thickness assumptions.
Point loads and anchorage needs can change the pad faster than the footprint does.

That is why the pad page keeps thickness starting points next to the live calculator.

Mistake 2

Confusing material quantity with full installed cost

Cost-intent searches are common here, but the first job is still to size the concrete correctly before labor and site work are layered on top.

Concrete quantity is only one part of the final project price.
Base prep, forms, reinforcement, delivery, and labor can outweigh a small material delta.

This page supports material planning first; it does not pretend to be a contractor bid engine.

Mistake 3

Jumping to bag counts without locking the base volume first

Bag totals are only trustworthy after the pad dimensions and thickness are fixed.

Start with length, width, and thickness to get the true base volume.
Only then compare 40, 60, and 80-lb bag counts and add waste.

The examples separate base volume from order-ready quantity so the bag count stays grounded.

Mistake 4

Using the pad page when the job is really a broader slab or a round pier

This page is for small rectangular pads. It is not the best fit for broader patio or driveway slabs, and it is definitely the wrong fit for cylindrical pours.

Use the slab calculator for broader flat pours like patios, walkways, and driveways.
Use the column calculator when the job is a pier, post hole, or sonotube.

Matching the calculator to the geometry is one of the fastest ways to avoid a bad order.