Concrete Pad Calculator
Calculate cubic yards of concrete for an equipment, AC, or hot tub pad from its length, width, and depth, plus material cost.
How this calculator works
An equipment pad — for an AC condenser, generator, or hot tub — is a small, straightforward rectangular pour. This calculator multiplies length, width, and depth to get cubic feet, then divides by 27 for the cubic yards you’d need, whether ordering bagged mix or a short ready-mix load.
Formula: Cubic yards = (Length ft × Width ft × Depth ft) ÷ 27.
Worked example
A 10 ft × 10 ft pad at a 4-inch depth:
- Depth in feet: 4 ÷ 12 = 0.3333 ft
- Cubic yards: (10 × 10 × 0.3333) ÷ 27 ≈ 1.23 yd³
- At $150/yd³, that’s $185.19 before waste.
Cost reference
| Pad size | Depth | Cubic yards | Cost at $150/yd³ |
|---|---|---|---|
| 5 ft × 5 ft | 4 in | 0.31 yd³ | $46.30 |
| 10 ft × 10 ft | 4 in | 1.23 yd³ | $185.19 |
| 20 ft × 20 ft | 4 in | 4.94 yd³ | $740.74 |
How to measure your pad
Measure the equipment’s actual footprint first, then add a few inches of margin on each side for the pad size you’ll pour — most equipment pads are much smaller than the 10 ft × 10 ft default shown here, so adjust the length and width down to match your unit before reading the result. Use the depth your equipment manufacturer specifies, or 4 inches as a general default for light equipment.
Frequently asked questions
What size pad does an AC unit or generator need?
Most residential AC condensers and standby generators sit on a pad only slightly larger than the unit's footprint — often 2-3 ft square to 4-5 ft square depending on the equipment. Check the manufacturer's installation manual for the required minimum pad size and clearance before pouring.
How thick should an equipment pad be?
4 inches is typical for light equipment like AC condensers, hot tubs (empty weight, since a filled hot tub's weight is spread by its own frame), and small generators. Heavier equipment — larger generators, HVAC package units — may call for a thicker pad or added reinforcement per the manufacturer's spec.
Should a small pad use bags or a ready-mix truck?
Small pads under roughly 1 cubic yard are usually cheaper and easier to mix from bagged concrete than to arrange a ready-mix delivery for, especially since many suppliers charge a short-load fee below their minimum order. Anything over about 1 cubic yard starts to favor ready-mix on labor alone — use the concrete bag calculator to compare bag count directly.
Does a pad need to be reinforced with rebar or mesh?
For light, non-structural equipment pads, many installers skip reinforcement or use a single layer of wire mesh for crack control. Pads supporting heavier equipment, or built in areas with poor soil, benefit from rebar — check the equipment manufacturer's mounting requirements and your local code.
Should the pad be larger than the equipment's footprint?
Yes — most installers pour the pad a few inches larger than the equipment on all sides, both for a cleaner installed look and to keep the unit's feet or mounting brackets fully supported rather than overhanging the edge.
Estimates only. Verify quantities with your supplier before purchasing.