Why the mound is a frustum and not a box
A mound is a circular pad with a flat table at the top and sloping ground everywhere else. The cleanest way to get a volume out of that is to convert the rectangular table into a circle of the same area and treat the whole thing as a truncated cone. The formula is pi times the height over three, times the sum of the outer radius squared, the outer times the inner radius, and the inner radius squared.
On the defaults — an 18 foot pad, a 5 by 3 foot table, 10 inches of height — the table is 15 square feet, which as a circle is 4.37 feet across. The volume comes to 92.0 cubic feet, which is 3.41 cubic yards. The table block on its own, 15 square feet times ten inches, is 12.5 cubic feet. So the table is 13.6 percent of the volume and 5.9 percent of the pad area, and the slope around it is everything else.
That is the number worth carrying away. When someone says a mound needs a few bags of clay, they are pricing the table. The mound is the skirt.
Two materials, not one
The body of the mound is mound mix, a high-clay soil placed in compacted lifts. The landing area in front of the rubber and the ground around home plate take packing clay, which is a much denser product supplied as bricks and laid like masonry. They are priced differently, they are handled differently, and mixing them up on an order is an expensive mistake in both directions.
Because the landing block sits inside the mound, this calculator takes its volume out of the mound mix figure rather than counting the same cubic feet twice. With the defaults the landing block is 4.0 cubic feet out of 92.0, leaving 88.0 cubic feet of mix, which after the bulking allowance is 3.75 cubic yards or 5.06 tons.
Brick counts and the season
Bricks come from volume divided by volume. A 6 by 4 by 2 inch brick is 48 cubic inches. The landing block at 4 by 3 feet and 4 inches deep is 4.0 cubic feet, which is 6,912 cubic inches, which is 144 bricks before waste and 159 at ten percent. The plate and box area at 6 by 4 feet and the same depth is 8.0 cubic feet, 288 bricks before waste and 317 after. That is 476 bricks for one build.
| Area | Size | Volume | Bricks at 10% waste |
|---|---|---|---|
| Landing | 4 x 3 ft at 4 in | 4.0 cu ft | 159 |
| Plate and boxes | 6 x 4 ft at 4 in | 8.0 cu ft | 317 |
| One build | 12.0 cu ft | 476 | |
| Two builds a season | 24.0 cu ft | 952 |
Brick dimensions are fields because they are not standard. Products differ, and a half inch on the thickness moves the count by a quarter. Measure one before ordering the season.
What moves the number most
Height, then diameter. Volume is linear in height, so going from 10 inches to 12 adds twenty percent. Diameter is squared inside the frustum formula, so the pad is the bigger lever of the two even though it feels like the less important dimension.
The bulking allowance matters more here than on a flat skin. Mound mix is placed in thin lifts and compacted hard, which is the whole point of it, and the height it loses in the process is substantial. Running out of mix at the third lift means coming back the next day and starting a new lift against a dried face, and that joint is where mounds later come apart.
What this page will not tell you
It will not give you a mound height, a slope, a table size, a distance to the plate, or the shape of the ramp. Those are rule-book dimensions, they differ by age group and by the organisation sanctioning your games, and they change. Take them from the document that governs your league and enter them here.
It also will not tell you whether a particular clay is right for your climate or your maintenance programme. That is a question for a sports turf agronomist and for the supplier who makes the product.
Why no dimension on this page is a specification
Every distance here is something you type in. That is deliberate. Base paths, arc radii, goal sizes, line widths, run-off margins and safety zones are not universal numbers: they differ between youth, high school, college and adult play, between the organisations that sanction those games, and between one facility standard and the next. A page that hard-coded any of them would be wrong for most of the people reading it and would sound authoritative while being wrong.
So the rule book that governs your league is the authority on the dimension, and the facility standard your grounds department works to is the authority on how much room goes around it. Measure the field you actually have, take the target dimensions off the document that governs your play, and put those numbers in the form. What this calculator does is the arithmetic that follows.
Before anything goes into the ground
Irrigation mains, drainage, electrical runs to scoreboards and lighting, and old utility crossings all live under sports fields, frequently at shallow depths and frequently not where the as-built drawing says. Call 811 before you dig, trench, drive a stake, auger a post or set an anchor, and give the locate time to be marked. Private lines on the facility side of the meter are usually not covered by the public locate service, which is what catches out a crew that did everything else right.
Open fields are also the place people get hurt by heat and by machinery. A groundskeeper on a mower or an aerator in July is exposed on both counts at once, and neither risk announces itself.
Related pages: the infield mix calculator covers the skinned area around the mound, the aeration and topdressing calculator handles the turf, and the topsoil calculator is the general bulk-soil tool. If you are also building a cage, the batting cage net calculator sizes the netting and the clearance.
Questions people ask
How much material does a pitching mound take?
Model it as a truncated cone. On an 18 foot pad with a 5 by 3 foot table at 10 inches above grade, the volume is about 92 cubic feet, or 3.41 cubic yards. Take out the packing clay block in the landing area and you are left with about 88 cubic feet of mound mix, which after a 15 percent bulking allowance is 3.75 cubic yards and around 5.06 tons at 1.35 tons a yard. Height and pad diameter are the two dimensions that move it.
How many clay bricks for a landing area?
Divide the block volume by the brick volume. A 4 by 3 foot landing area at 4 inches deep is 4.0 cubic feet, which is 6,912 cubic inches. A 6 by 4 by 2 inch brick is 48 cubic inches, so that is 144 bricks, or 159 with ten percent waste for cutting and breakage. Brick sizes differ between products, so measure one rather than assuming.
What is the difference between mound mix and packing clay?
Mound mix is a high-clay soil placed and compacted in lifts to build the body of the mound. Packing clay is a much denser product supplied as bricks, laid into the landing area in front of the rubber and around home plate where cleats do the most damage. Packing clay is far more expensive per cubic foot and is used only in the wear blocks, not through the whole mound.
How often does the landing area need rebuilding?
That depends entirely on how much the field is used, at what level, and in what weather, so the number of rebuilds is a field here rather than an assumption. Two a season is a common starting point for a field with a normal schedule. What is worth doing is pricing the season rather than the build, because the brick order for a year is usually the larger number and it is the one that has to fit a budget.
Why does the calculator convert the table to a circle?
Because a truncated cone has a closed-form volume and a rectangle-on-a-circle does not. Converting the table to a circle of equal area lets the whole mound be treated as one frustum, which is accurate to within a few percent for normal proportions. It is an approximation and the page says so. If you want a floor on the answer, the table block on its own is a number the result also shows, and no mound contains less than that.