Fence Post Calculator
— How Much Do You Need?

This is one of the most common questions homeowners ask before starting a fencing project, and the answer depends on your fence type, your soil, and how long you want your posts to hold up. Concrete gives posts a rigid hold, which makes it a reasonable choice for gate posts or any post that will take heavy lateral stress from a swinging gate or tensioned fence line. However, concrete has a serious downside when it comes to wood posts. It traps moisture right at the soil line, which is exactly where rot begins. When water collects around the base of a wooden post and has nowhere to drain, the post can degrade from the inside out in just a few years. Gravel solves that problem. When you pack clean crushed stone around your posts, water drains through the material rather than pooling against the wood. This keeps the base of the post drier and dramatically extends its lifespan. Many experienced fence builders use a combination approach: a layer of gravel at the bottom of each hole for drainage, concrete fill for structural strength, and a gravel cap at the top to channel surface water away from the post. For lighter fences, like garden fencing or decorative picket fences, well-compacted gravel alone can be enough to hold a post firmly. If you are working on a longer fence line or a full property boundary, Hello Gravel can deliver the bulk crushed stone you need right to your site.

The standard rule of thumb is to bury one-third of the post's total length underground. For a fence with 6-foot panels above ground, that means setting your posts at least 2 feet deep. For an 8-foot fence, plan on at least 2.5 to 3 feet below grade. If you live somewhere with cold winters, depth matters for another reason entirely. When the ground freezes and thaws repeatedly, it can push shallow posts right out of the ground over time. This is called frost heave, and it is one of the most common causes of fence failure in northern climates. Burying your posts below your local frost line prevents it. Frost depths range from just a few inches in the South to 4 feet or more in parts of the upper Midwest and New England, so check what your local frost depth is before you start digging. Going too shallow is the single most common fence installation mistake. A post without enough ground contact cannot resist the lateral pressure that wind, soil movement, and the weight of fence panels put on it over time. Getting the depth right from the start saves you from dealing with a leaning or failing fence just a few years down the road. Depth also directly affects how much gravel you need. Every extra inch of depth adds volume to each hole you need to fill. The Hello Gravel calculator lets you plug in your hole diameter, depth, and post count to get an accurate material estimate before you order.

Not all gravel behaves the same way in a post hole, and the type you choose makes a real difference in how well your posts hold up. Clean crushed stone is one of the best options for fence post installation. Because the pieces are angular and irregular, they lock together when you compact them, which gives the material good lateral stability around the post. Crushed stone also drains freely, keeping moisture away from the wood and reducing the conditions that lead to rot. Pea gravel is another solid choice. It is smooth and easy to work into tight spaces around a post, and the rounded stones create natural void space that lets water drain through quickly. The tradeoff is that pea gravel does not interlock the way angular stone does, so it provides less structural support on its own. It is an excellent drainage material but is better used at the bottom of the hole or as a top layer rather than as the primary fill. What you want to avoid is any gravel with a high proportion of fine material, like stone dust or heavy screenings. Those fines compact into a dense layer that holds moisture rather than releasing it, which defeats the whole purpose of using gravel in the first place. For most fence post applications, clean crushed stone gives you the best combination of drainage and stability. If you are not sure which product fits your project, reach out to the Hello Gravel team and we can point you in the right direction.

Your total quantity depends on three things: the number of posts you are setting, the diameter of your post holes, and how deep you are digging. Here is a practical way to think about it. A standard post hole is about 8 to 10 inches in diameter. At a burial depth of 2.5 feet, each hole holds approximately 1.1 to 1.4 cubic feet of space after accounting for the post itself. That does not sound like much per hole, but it adds up fast across a full fence line. For a 100-foot fence with posts spaced 8 feet apart, you are working with roughly 13 to 14 posts. At about 1.2 cubic feet of gravel per hole, using a 10-inch diameter hole at 2.5 feet of depth as the baseline, you would need around 16 to 17 cubic feet of gravel for the post holes alone. For a 400-foot fence line, that figure multiplies to roughly 65 to 70 cubic feet, or just over 2 cubic yards. Keep in mind that many fence projects use gravel for more than just the post holes. Running a drainage layer along the base of the fence line, creating a clean gravel border around the perimeter, or prepping a gate area all add to your total. Ordering a truckload covers your post holes and gives you material for those other uses without making multiple trips. The Hello Gravel calculator is the fastest and most accurate way to determine how much to order for your specific project. Plug in your dimensions and it will give you a clear quantity recommendation.

Yes, and in many situations, gravel-set posts actually hold up better over time than posts set in concrete. The key is proper compaction. You cannot simply pour gravel into a hole and move on. The right method is to add gravel in 4 to 6 inch layers, tamping each layer firmly before adding the next. Using clean crushed stone rather than smooth rounded stone gives you better compaction and more resistance to lateral movement. Done correctly, this creates a firm, well-draining base that holds the post securely. Gravel-set posts are especially practical in two situations. First, if your soil is naturally well-draining, the compacted gravel locks into the surrounding ground and provides solid support. Second, and this is a real practical benefit, gravel-set posts are much easier to remove or replace if you ever need to. There is no concrete to break out. You can pull the post and clear the hole in a fraction of the time it would take with a concrete-set post. That said, certain posts should still be set in concrete. Gate posts carry repeated swinging force that gravel alone may not handle as reliably over many years. Corner posts on tensioned wire fences also benefit from the rigidity concrete provides. For standard line posts on privacy fences, wood panel fences, or picket fences, well-compacted gravel is a proven, long-lasting option that many professional fence builders prefer for exactly the drainage and serviceability reasons described above.