Generator Pad Calculator
— How Much Do You Need?

For a generator pad, you want a material that compacts firmly, drains well, and holds its position under the weight of the equipment. Angular crushed stone is a top choice because the irregular edges of each piece lock together when compacted, creating a surface that resists shifting. Common options like #57 or #67 crushed stone work well for this reason. Crusher run, also known as dense-graded aggregate or road base, is another excellent option. It contains a blend of particle sizes that compact into a near-solid base, which is especially useful if you need a very stable, level surface. Rounded materials like pea gravel are not a good fit for generator pads. Because the stones are smooth and uniform, they roll and migrate instead of locking together, and that movement can leave your generator sitting unevenly over time. If you are unsure which material fits your project best, the Hello Gravel team is happy to walk you through the options. Just reach out and describe your setup.

The right size depends on your generator's footprint plus a margin of extra space on every side. A good general rule is to extend the pad at least 6 inches beyond the generator frame in all directions. This gives the base edge enough stability to resist erosion and settling at the perimeter. For smaller standby generators in the 7 to 20 kilowatt range, a pad around 3 feet by 5 feet is common. Larger whole-home generators in the 20 to 30 kilowatt range often need a pad closer to 4 feet by 6 feet or larger. Commercial and industrial generators can require significantly more space depending on the unit and how it is mounted. Always check your generator manufacturer's installation manual before you build. Most manufacturers specify minimum pad dimensions, and your generator installer can give you a precise recommendation based on the specific unit you are working with. Starting with the right dimensions means you will not have to rework the pad later.

To estimate how much gravel you need, multiply the length, width, and depth of your planned pad to get the total volume. For example, a 4-foot by 6-foot pad at a compacted depth of 6 inches comes out to roughly half a cubic yard of material. Because Hello Gravel delivers bulk aggregate by the truckload, a generator pad on its own represents a small portion of a full delivery. Most customers get the best value by ordering their generator pad gravel alongside another project happening at the same property, such as a driveway refresh, a shed base, a drainage improvement, or a landscaping project. That way, the truckload is put to full use and you get everything delivered in a single trip. Contractors who install generators regularly often order for several jobs at once, which makes bulk delivery a natural fit. If you run a contracting operation, Hello Gravel's HG Pro membership is worth a look. It is designed for high-volume and recurring orders and can simplify your process considerably. Use the Hello Gravel calculator on this page to get a precise quantity estimate based on your exact dimensions, then contact our team to talk through how to structure your order.

Most generator installations call for a minimum of 4 inches of compacted gravel, but 6 inches is a better target if your soil is soft, clay-heavy, or prone to movement when it gets wet. A deeper base gives you more stability, improves drainage away from the unit, and creates a longer-lasting foundation overall. If you are in a region that experiences hard freezes in winter, going to 6 inches or deeper is especially smart. Frost heave, which happens when moisture in the soil freezes and expands, can push a shallow base out of level and tilt your generator over time. A deeper base helps protect against this. Your generator manufacturer's installation guide will typically specify a minimum depth requirement as part of the warranty conditions, so it is worth checking that document before you start digging. When in doubt, go a little deeper rather than a little shallower.

Yes, and this step matters more than most people expect. Skipping proper ground prep is one of the main reasons generator pads settle unevenly over time. Start by clearing the area of grass, weeds, roots, and any organic material. Organic matter breaks down as it decomposes, which causes the ground beneath your pad to sink and shift. Once the area is cleared, excavate down to the depth you need for your gravel base. If the subsoil feels soft or loose, compact it with a plate compactor or hand tamper before you add any gravel. A layer of landscape fabric at the base of the excavation can help prevent weeds from pushing up through the gravel later. When you add the gravel, do it in layers of about 2 to 3 inches at a time and compact each layer before adding the next. This layered approach produces a much firmer and more level pad than dumping all the material in at once and tamping it down in a single pass. Taking your time on these steps pays off in a pad that stays flat and stable for years.