Stone Calculator for Drains, Pads and Graded Sizes
Enter your project dimensions
The decision in front of most people who open this page is not how many tons. It is whether this layer should let water through or lock up hard, and in Virginia the ground answers that before the tape comes out. Get it the wrong way round and the tonnage is beside the point: fines in a French drain hold the water you were trying to move, and clean stone under a pad keeps shifting under the load.
What the ground under the layer is telling you to order
Decision criterion: is water the problem, or is load the problem?
- Flat Coastal Plain ground in Hampton Roads, on the Eastern Shore and across the Northern Neck sits low, with water close to the surface and nowhere for a storm to run. Water is the problem. Clean, washed stone stays open and keeps moving it, and the layer wants to sit above the surrounding grade rather than in a dish.
- Piedmont clay, often red, takes water in slowly and sheds the rest across the surface. Both problems are live at once. The base carries the load in stone with fines, and the drainage runs in clean stone alongside it, wrapped in non-woven fabric so the clay does not migrate into the voids.
- Limestone valleys west of the Blue Ridge often put rock within a foot of the surface, so an excavation can finish shallower than planned. Measure what you actually achieved and enter that. Spread runoff rather than concentrating it in one place on karst ground.
Frost is set locality by locality here, from about 12 inches at the coast to about 24 in the northern counties, so check your own figure rather than a statewide one, and treat drainage rather than depth as the defense against heave.
Size numbers, and what each one is for
Lower numbers mean larger stone. On this site the graded sizes run from #4 Crushed Stone at 3/4 to 1-1/2 inches down through #57 Stone at 3/16 to 1 inch, #67 Stone at 1/4 to 3/4 inch, #8 Crushed Stone at about 3/32 to 3/8 inch and #89 Crushed Stone from 3/8 inch down to fines.
Virginia suppliers often call #57 three-quarter inch stone, and 3/4" Crushed Stone is the same size sold under the name people ask for. Screenings are chips and dust together, which screed and firm into a leveling course. Railroad Ballast is heavy angular stone for equipment pads, construction entrances and farm tracks that stay wet.
If a plan or a permit names a gradation, order that gradation. If the words on the plan and the words in the catalog do not match, ask through the contact page before ordering rather than picking the nearest-sounding name.
Trench width rather than pipe width, and the rest of the controls
Rectangle takes a length and a width in feet, which is how a trench goes in: run length by trench width, not by pipe diameter. Circle takes a diameter in feet, which suits an outfall apron or a ring around a structure. Multiple areas holds up to five entries, so a drain line, a splash pad and a strip of bedding can be totaled in one go.
Depth (inches) accepts 0.25 to 24. A trench deeper than two feet goes in as two entries, the lower part and the upper part, and the results are added. The material select converts volume to weight, and it has to match what you are actually ordering. The tick box adds 5 per cent for compaction and spillage; it is optional, and it is the only extra-quantity control on the page. Results come back as cubic yards, tons and cubic feet, and Email my quote sends them to you.
The weights behind the ton figure
The yardage never moves. The tons do, because each family is published at its own weight: #57, #67 and 3/4 inch stone at about 2,800 lb a cubic yard, which is 1.4 tons; #8, #89 and 3/8 inch chips at the same 2,800; screenings and #4 stone at about 2,900, or 1.45 tons; dense-graded base at about 3,000, or 1.5; and rip rap heaviest at about 3,100, which is 1.55.
The practical effect is small per yard and real per order. Ten yards of #57 is 14 tons, the same ten yards of screenings is 14.5, and the same ten yards armoring a bank is 15.5.
A 46-foot drain line across a Henrico back yard
Hypothetical work, with the arithmetic shown. The trench runs 46 ft, is 12 inches wide and is backfilled 18 inches deep with clean stone over a perforated pipe.
Area is 46 x 1 = 46 square feet. Eighteen inches is 1.5 ft, so 46 x 1.5 = 69 cubic feet. Divide by 27 for 2.56 cubic yards, and at 1.4 tons a yard that is 3.58 tons of #57. Round to 3.75. A 4-inch pipe running the length of it displaces well under a tenth of a yard, so calculate the trench rather than the trench minus the pipe, and place the small remainder at the outfall.
Two more from the same yard. A shed pad finished with a leveling course of screenings, 12 by 16 ft at 1.5 inches: 192 x 1.5 / 12 = 24 cubic feet, 0.89 cubic yards, 1.29 tons at 1.45. A construction entrance in #4 stone, 30 by 14 ft at 6 inches: 420 x 0.5 = 210 cubic feet, 7.78 cubic yards, 11.28 tons at 1.45.
Ordering a surplus that has somewhere to go
Angular stone under traffic gives up 5 to 10 per cent of its loose depth as it settles, which is what the optional 5 per cent covers on routine work. Where a compacted depth is specified, build the allowance into the depth you enter instead, and let the tick box handle spillage only.
Round up where the surplus has a home: a drain outfall, a soft spot in an entrance, the edge of a pad. Round down on decorative infill and small bedding runs, where a quarter ton has nowhere to go but the side of the lawn.
This page covers stone specified by size number. Surfacing families sold by their job rather than their gradation, including driveway and walkway gravel, are converted on the gravel calculator, and dense-graded base is sized on the road base calculator. Once the tonnage is settled, open the product page, set your quantity and date, and delivery is arranged at checkout by ZIP code.
Common questions
Does the border or edging strip count as part of the area I measure?
Measure to the inside of whatever is retaining the stone, because that is what the layer fills to. Where a drain trench is lined with fabric, the fabric follows the trench walls and takes up no measurable volume, so the trench dimensions stand as measured.
The drive needs a base and a surface course. Is that one calculation or two?
Two, and they are different materials at different weights. Size the dense-graded base at its compacted depth on its own page, then come back and size 2 inches of #57 or another clean surface stone here. Adding the depths together and running one figure would convert the whole lot at one weight and put the wrong stone on half the order.
The bed I am filling is a curved sweep rather than a rectangle. What do I enter?
Cover it with two or three rectangles that overshoot the bulges by roughly as much as they miss the hollows, and enter them under multiple areas. Stone beds are shallower at the edges as a rule, so slightly generous rectangles usually come out close.
The existing stone has thinned in the wheel tracks. How much do I order to bring it back?
Only the depth that has gone. Rake the surface level, measure down from a straightedge in several places along the tracks, and enter that average, which on a worn surface course is commonly 1 to 2 inches. The area stays the full area, since a patched strip rarely blends in.
What goes wrong if the order lands half a ton short?
On a drain, the top of the trench finishes low and the fabric fold has nothing to sit against. On a pad, one corner stays thin and starts working loose under the first load. Stone is easy to place as a surplus and awkward to add in small amounts later, so on anything that will carry weight, take the higher of the two round figures.
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