Stone Calculator for Trenches, Bedding and Drain Lines
Enter your project dimensions
Most of the stone on this page ends up out of sight. It goes down a trench behind a wall, under a length of pipe, along a drain line cut through Piedmont red clay that holds water for a week after a storm. That makes the measuring harder than it looks, because a trench is not a patio and a ring around a fire pit is not a rectangle at all. The stone calculator above will turn your feet and inches into tons exactly, but only for the shape you describe to it, so the description is worth getting right first.
Trenches, rings and side yards: getting a footprint off awkward ground
A trench is a long, narrow rectangle. Measure the run in feet along the bottom of the cut, then put the trench width in as a decimal of a foot: a 12-inch trench is 1, an 18-inch trench is 1.5, a 9-inch one is 0.75. The depth you enter is the depth of stone, not the depth of the hole, which matters as soon as a pipe or a layer of fabric takes up part of it.
A ring goes in as a circle, measured straight across the middle. If the ring surrounds something, work out the full circle and accept the small overage, or subtract the middle as a second calculation and take the difference.
Separated patches are what the multiple-areas mode is for. Three downspout pits, a strip along the shed and a short run beside the drive add up to one order, and the tool takes up to five areas in one pass. Sketch them before you start typing and write every reading as a decimal so nothing gets rounded twice.
Lower numbers mean bigger rock, which is where orders go wrong
The grade number describes a size range, and it runs backwards from what most people assume. #4 crushed stone is the coarse one at 3/4 to 1-1/2 inches. #57 stone is a 3/16 to 1 inch general-purpose washed stone used in drains, driveways and concrete work. #67 stone is finer at 1/4 to 3/4 inch and is the usual choice under pipe. #8 crushed stone sits around 3/32 to 3/8 inch, and #89 crushed stone starts at 3/8 inch and carries fines, which suits joints and finish courses. Screenings are chips and dust together, screedable and compactable. Railroad ballast is angular stone of 1 to 2.5 inches for loads sitting on wet ground.
The split that matters is washed against binding. Clean washed stone lets water through, which is why a drain gets #57 or drain rock and never a material with fines in it. ABC stone and crush and run bind when rolled, which is what a lane wants and what a French drain cannot tolerate. If the job is the running surface of a drive or a parking pad, the gravel calculator is built around that; this page is for stone ordered by its number.
Handing the stone calculator a trench, a ring and three patches at once
Pick Rectangle, Circle or Multiple areas across the top. Length and Width go in as feet, or Diameter if you chose a circle, and you can add up to five areas before the total is returned. Depth goes in as inches and the box accepts anything from 0.25 to 24, so a half-inch skim and a two-foot backfill are both inside its range. Set the Material to the grade you are actually buying, because that select is what decides the weight applied.
The tick labeled "Add 5% extra for compaction & spillage" is the only allowance the form offers, and it is optional. Leave it on for anything angular that will be rolled or walked in. Press Calculate material needed and the result comes back as cubic yards, tons and cubic feet at once. "Email my quote" sends the figures to you with the measurements attached, which is worth doing if the stone is going in on a different day from the digging.
Two inches of topping, a foot of drain stone, and what sits between
Depth is doing more work than area on almost every job here. A finish or topping course is 2 to 3 inches. A base under something is 4. A French drain is 12 inches or more of clean stone around the pipe, and wall backfill is often deeper still.
That last case runs into the ceiling. Anything past 24 inches has to go through in two passes, so calculate the bottom two feet, calculate the remainder, and add the yardages yourself. The form will not carry it over for you.
Why a foot of screenings bills heavier than a foot of #57
Volume answers how much hole you have. Tons answer what comes off the truck, and the two only connect through a weight figure. The washed grades this site publishes, #57 and #67 and 3/4 inch and the 3/8 inch chips, all work out at roughly 2,800 lb a cubic yard, which is 1.40 tons. Screenings and dust are heavier at about 2,900 lb, or 1.45, and #4 stone and railroad ballast share that same 1.45. Crush and run and ABC stone reach about 3,000 lb, or 1.50, and armor stone is heaviest at roughly 3,100 lb, or 1.55. Those are approximate figures and they are the ones the site works to.
Coverage falls out of the same arithmetic. A ton of material at 1.40 spreads over about 116 square feet at 2 inches, 77 at 3 inches and 58 at a 4-inch base depth. Switch the material select from #57 to screenings on an identical trench and the yardage will not move at all while the tons will.
A 40-foot drain line below a clay bank, and a dog run beside the shed
Both of these are illustrative, not customer work.
The drain runs 40 feet along the low side of a clay bank, cut 12 inches wide, with 12 inches of #57 around a 4-inch pipe. 40 x 1 = 40 square feet. 40 x 12 / 12 = 40 cubic feet. 40 / 27 = 1.48 cubic yards. At 1.40 tons a yard that is 2.07 tons, or 1.56 yards and 2.18 tons with the five percent left on. The pipe displaces about 0.13 of a cubic yard, which is a wheelbarrow load, so take the full figure and tip the remainder at the outfall. Line the cut with non-woven fabric first or red clay will work its way into the voids and the drain will slowly stop draining.
The dog run behind the shed is 16 by 9 feet with 3 inches of #89 over a compacted subgrade. 16 x 9 = 144 square feet. 144 x 3 / 12 = 36 cubic feet. 36 / 27 = 1.33 cubic yards, which is 1.87 tons at 1.40. Had the same pen been surfaced in screenings instead, the yardage would still read 1.33 and the tons would come back as 1.93.
Taking the number to the grade you specified, not the one nearest to hand
Once the tons are on screen, open the product page for the exact grade and set a quantity and a date there. Delivery is arranged at checkout by ZIP code, and the driver needs a clear run to the spot where the pile can go down. If a plan or a permit names a gradation, buy that gradation: "3/4 clean" and #57 are often the same stone under two names, but the only way to be sure is to check the line item before ordering rather than after. The full stone list is worth a look if the spec is unfamiliar, and the contact page is there if a label on a drawing does not match anything you recognize.
Common questions
Drainage stone is going along two walls that meet at a corner. Can I total both runs in one entry?
Use Multiple areas and enter each run as its own rectangle, taking care not to count the corner twice. Measure the first run right through the corner and start the second run where the first one ended. The tool adds the areas and returns one yardage and one tonnage for the pair.
A row of cobbles edges the trench. Is that width part of what I type in?
Only if stone is going underneath them. Measure the width the drainage stone actually occupies, which usually stops at the inside face of the cobbles. On a narrow trench that edging can account for a quarter of the apparent width, and entering it inflates the order noticeably.
The pad needs a compacted layer under the washed stone. Is that one entry or two?
Two, with the material select moved between them. The bound layer weighs 1.50 tons a cubic yard and the washed topping 1.40, so a single run at either figure would be wrong for the other. They also arrive as two separate products, ordered from two pages.
The drain follows a curve around the back of the house. What length do I use?
Walk the line with a tape laid along the actual route rather than measuring the straight distance between the ends. A curve adds real length, and on a run of any size that is a quarter of a ton nobody accounted for. Enter the walked length with the trench width as usual.
The stone path has thinned out in patches. What depth do I enter to bring it back?
The depth of new material only. Lay a straight board across the worn section, measure down to the existing surface in two or three places and average what you find. An inch and a half is a common answer, and the depth box goes down to a quarter of an inch, so there is no need to round it up to something tidier.
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