AC Pad Calculator
— How Much Do You Need?

An AC pad is a flat, stable base that sits beneath your outdoor air conditioner condenser unit. Its job is to keep the unit level, supported, and protected from the ground beneath it. Your condenser is heavy. Most residential units weigh between 100 and 300 pounds, and they sit outside year-round through rain, frost, and heat. Without a proper base, the soil under the unit can erode or shift, causing the unit to tilt. Even a slight tilt puts stress on the refrigerant lines and the internal components, which can lead to premature wear or a costly repair. Gravel is one of the most popular materials for an AC pad because it compacts firmly, drains water away naturally, and holds its shape for years with minimal upkeep. Unlike bare soil, a well-built gravel pad will not wash out after a heavy rain or heave during a freeze-thaw cycle. It gives your equipment a reliable foundation and helps it run the way it was designed to.

Crushed stone is the go-to choice for most AC pad projects. Angular crushed gravel, such as 3/4-inch crushed stone, has edges that lock together when compacted. That interlocking action creates a firm, stable surface that resists shifting under the weight of the unit and holds up well through wet and freezing conditions. Pea gravel is another option if you prefer a rounder, cleaner look around the base of your unit. It drains exceptionally well and is easy to work with. The tradeoff is that pea gravel does not compact as tightly as crushed stone, so it works best under lighter units on ground that is already fairly stable. For most homeowners, crushed stone is the stronger long-term choice. If you are unsure which material fits your specific unit size and soil conditions, reach out to the Hello Gravel team and we can point you in the right direction.

A standard residential AC pad runs about 3 feet wide by 3 feet long, with a gravel depth of 4 to 6 inches once compacted. At 4 inches deep, that footprint requires roughly 0.3 cubic yards, or just under 500 pounds of gravel. At 6 inches deep, you are looking at closer to 0.5 cubic yards. These are small amounts on their own, and Hello Gravel delivers material by the truckload. Most customers who order for an AC pad roll it into a larger project so they get the most out of a single delivery. If you are planning a driveway refresh, a drainage channel, a garden path, or any other gravel work around your property, it makes good sense to calculate all of it together and place one order. Use the Hello Gravel calculator to enter your pad dimensions alongside any other projects you have in mind. It will give you a precise quantity estimate so you know exactly how much to order. If the numbers raise any questions, the Hello Gravel team is happy to walk through it with you.

Building a gravel AC pad is a manageable DIY project that most homeowners can finish in a single afternoon. Start by marking out the pad area. It should extend a few inches beyond the footprint of your condenser unit on all sides, so a 36-inch by 36-inch square is a common target. Then excavate the area to a depth of 4 to 6 inches, removing all grass, roots, and soft or loose soil until you reach firm ground. Once the area is dug out, you can lay a sheet of landscaping fabric across the bottom to keep fine soil from working its way up into your gravel layer over time and to discourage weed growth. This step is optional, but it helps the pad stay cleaner and more stable over the long run. Next, fill the excavated area with your crushed stone in layers of about 2 inches at a time, tamping each layer down firmly before adding the next. A hand tamper works fine for a pad this size, though a plate compactor will give you a more uniform result if you have access to one. Your finished surface should be level and solid with no soft or spongy spots. Set your condenser unit on the completed pad and check that it sits level. Most manufacturers recommend the unit be within a degree or two of level for the system to operate correctly, so take a moment to adjust the gravel beneath it if needed before the unit is fully connected.

Most HVAC manufacturers recommend at least 18 to 24 inches of clearance between the condenser unit and any wall, fence, or structure. Your condenser pulls air in from the sides and exhausts heat upward, so it needs open space around it to breathe. When airflow is restricted, the unit has to work harder to do the same job, which drives up your energy bills and puts extra strain on the compressor over time. Beyond clearance, think about where water tends to run around your home. You want your gravel pad in a spot that drains well and does not collect runoff from your roof or downspouts. Placing the pad in a low spot or directly under a drip edge will cause water to pool around the unit, which is hard on the equipment regardless of how good your pad material is. Your unit's installation manual will have the manufacturer's specific clearance requirements, and those numbers take priority over general guidelines. When in doubt, give the unit more space rather than less.