Can I calculate a round concrete pad?
Yes. Select circle, enter the diameter and thickness, and the calculator uses the circular volume formula: π × (diameter ÷ 2)² × depth.
Rectangle and circle pads
Concrete Pad Calculator
100% Free — No Sign Up Required
Choose a square or round shape, enter your dimensions, and calculate concrete for any pad in cubic yards, bags, or cubic meters.
Cubic yards
2.44
Cubic feet
66.00
Cubic meters
1.87
Estimated bags
110
Includes a 10% waste factor. This estimate is for planning only; forms, subgrade and delivery conditions can change the final order.
Quick Cost Estimate
Estimated total cost
$378.89
Quick Cost Estimate multiplies estimated cubic yards by your unit price. It excludes labor, delivery, pumping, reinforcement, base prep and tax.
How to Use the Concrete Pad Calculator
Start by picking the pad shape. Choose rectangle for square or rectangular forms and enter the length and width; choose circle when the diameter is the dimension you know, such as a round pier cap or a circular equipment base. Then enter the pad thickness in inches and a waste factor — 5–10% covers most small pours. The concrete pad calculator instantly converts your inputs into cubic yards, cubic feet, cubic meters, and an estimated bag count, so you can decide between ready mix and bagged concrete before you buy anything. Every input supports both imperial and metric units through the toggle beside the field, which makes it easy to calculate concrete pad volume from a metric spec sheet or a tape measure in feet.
Concrete Pad Formula: Square vs Round
A rectangular pad uses the same formula as a slab: length × width × (depth ÷ 12) gives cubic feet, and dividing by 27 gives cubic yards. A round pad replaces the area term with a circle: π × (diameter ÷ 2)² × (depth ÷ 12). The difference matters — a common shortcut is to treat a round pad as a square, which overestimates the concrete by more than 20%, since a circle covers only about 78.5% of the square that contains it. This concrete pad estimator applies the correct formula for whichever shape you select. For example, a 6 ft round pad at 4 inches deep needs π × 3² × 0.333 = 9.4 cubic feet, about 0.35 cubic yards, while a 6 × 6 ft square pad at the same depth needs 12 cubic feet. If the pour is a large rectangular floor rather than a small pad, the concrete slab calculator is the better starting point.
Common Concrete Pad Uses
Most pad projects are small, single-purpose pours. A shed base is typically 4 inches thick and sized a few inches larger than the shed footprint on each side. A hot tub pad usually needs 4 to 6 inches of concrete because a filled spa can weigh several tons concentrated on a small area. An AC condenser pad is often 3 to 4 inches thick and only slightly larger than the unit itself. Generator pads, heat pump pads, and trash can pads follow the same pattern: modest area, moderate thickness, and easy access for hand mixing. Because these pours are usually well under one cubic yard, bagged concrete is the practical choice — the concrete bag calculator converts any pad volume into a shopping list of 40 lb, 60 lb, or 80 lb bags.
Tips for Pouring a Pad
Excavate a few inches deeper than the pad and add compacted gravel so the concrete rests on a stable base rather than raw soil. Check the forms for level and square before mixing, because a pad that holds equipment must drain away from buildings while staying flat enough for the unit to sit correctly. Mix bags in batches and keep a consistent water ratio — too much water weakens the surface. For pads larger than about ten 80 lb bags of volume, compare the cost of a short-load ready mix delivery using the Quick Cost Estimate under the calculator; enter a price per cubic yard and it returns a material-only total you can weigh against bag prices.
Concrete Calculators by Project Type
Concrete Slab Calculator
Use length, width and thickness for floors, patios and rectangular slabs.
Concrete Pad CalculatorEstimate square, rectangular or circular pads with a quick cost field.
Concrete Yard CalculatorConvert dimensions into cubic yards, cubic feet and cubic meters.
Concrete Bag CalculatorEstimate 40 lb, 60 lb and 80 lb bags after waste is added.
Frequently Asked Questions
How thick should a concrete pad be?
AC pads are commonly 3–4 inches, shed bases 4 inches, and hot tub or generator pads 4–6 inches. Heavier loads and soft soil call for a thicker pad.
How many bags do I need for a 4x4 pad?
A 4 × 4 ft pad at 4 inches thick is about 5.3 cubic feet. With 10% waste that is roughly 10 of the 80 lb bags or 13 of the 60 lb bags.
What waste factor should I use for a pad?
Five to ten percent is a common starting range. Use more if the base is uneven or the forms are hard to fill cleanly.