Stone Calculator for Trenches Dug in the Dry Season
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Drainage work gets planned around the calendar here, because an open trench in the middle of the wet season fills from the bottom before you have finished lining it. Most of this work lands between November and April in the south of the state and in the gaps between fronts further north, which means the material has to be ordered ahead and has to be right first time. This stone calculator turns the hole you are about to dig into a tonnage, but only after the tape has been honest about what shape that hole really is.
Taping a trench along the slab and a ring at the well head
A drainage run is a long, narrow rectangle and it gets measured as one: the length of the run, the width of the trench at the bottom, and the depth of stone rather than the depth of the excavation. Do not take the pipe out of the volume. A four-inch line through a foot-wide trench displaces less than a wheelbarrow load over a typical run, and the arithmetic to remove it is not worth the risk of coming up short with the trench open.
A ring of stone around a well head or the collar at the base of a downspout is a circle, measured across the widest point. Where a run steps out around a slab corner or a pool deck, treat each straight leg as its own rectangle and stop one where the next begins, so the corner is counted once.
Three splash pads, a well-head ring and a trench in one stone calculator run
Rectangle takes a length and a width in feet, circle takes one diameter in feet, and multiple areas totals as many as five pieces in a single calculation. The depth field is in inches and accepts anything from a quarter inch to 24, and one depth covers the whole run, so a 14-inch trench and a 3-inch splash pad go through separately.
That 24-inch ceiling matters on deep work. A trench taking three feet of stone gets entered as two runs and the tonnages added, which is safer than converting to feet somewhere in your head and losing a factor of twelve.
The material line picks the grade and sets the weight behind the tons reading. The checkbox adds an optional 5 percent for compaction and spillage. The results panel returns cubic yards, tons and cubic feet together, with a button to email the figure to yourself.
Depth by what the layer is doing, not by what it looks like
A surface or topping course runs 2 to 3 inches. A structural layer under pavers or a pad goes 4 inches compacted. A French drain wants 12 inches of clean stone or more, because the void space in that stone is the storage the system relies on, and a shallow trench in sandy ground simply passes the water back into ground that is already saturated.
Grade numbers run backwards from what people expect: the lower the number, the larger the rock. #4 is 3/4 to 1-1/2 inches, #57 runs 3/16 to 1 inch and is the general-purpose drainage and concrete size, #67 is finer at 1/4 to 3/4 inch and is common around pipe, #8 is about 3/32 to 3/8 inch, and #89 runs 3/8 inch down to fines for joints and finish courses. Screenings are dust and chips that compact to a firm screeded surface. Railroad ballast is angular stone from 1 to 2.5 inches for hard standing and heavy loads.
The split that actually matters is clean against fines. Washed stone such as #57 stays open and lets water through. A graded mix with fines binds under compaction and is a base material. Put the mix in a drain and it silts up; put clean stone under a drive and it keeps moving. Where a permit or a drawing names a gradation, build to that.
One volume, six weights, and the line that turns yards into tons
Cubic feet is the footprint in square feet times the depth in inches, divided by 12. Cubic yards divides that by 27, because a cubic yard is a three-foot cube and that is how bulk stone is hauled. Tons applies the published weight of whichever grade you selected, and this is where the grades part company.
| What you selected | Per cubic yard | Tons per yard |
|---|---|---|
| #57, #67 or 3/4 inch crushed stone | about 2,800 lb | 1.40 |
| #89, #8 or 3/8 inch chips | about 2,800 lb | 1.40 |
| Stone screenings or dust | about 2,900 lb | 1.45 |
| #4 stone or railroad ballast | about 2,900 lb | 1.45 |
| Graded base mix with fines | about 3,000 lb | 1.50 |
| Rip rap | about 3,100 lb | 1.55 |
Same trench, same depth, different line selected, different ticket. The figures are approximate and drift with how wet the material is, but the volume you ordered has not changed.
A 36-foot drain on a lot that ponds, and a shed pad capped in screenings
Hypothetical jobs, worked longhand.
The drain runs 36 feet at a trench width of 12 inches, filled with 14 inches of #57. A one-foot width makes the footprint 36 square feet. 36 x 14 = 504, divided by 12 is 42 cubic feet, divided by 27 gives 1.56 cubic yards. At 1.40 tons to the yard that is 2.18 tons, or about 1.63 yards and 2.29 tons with the 5 percent ticked. Wrap the trench in non-woven fabric before the stone goes in. In sand that wrap is what keeps the voids open, and without it the drain silts from the outside in.
The shed pad is 10 by 12 feet, so 120 square feet, and it goes down in two courses. Four inches of #57 as the structural layer: 120 x 4 = 480, divided by 12 is 40 cubic feet, divided by 27 is 1.48 cubic yards, or 2.07 tons. Two inches of Stone Screenings capped over it: 120 x 2 = 240, divided by 12 is 20 cubic feet, divided by 27 is 0.74 cubic yards, and at 1.45 that is 1.07 tons. Two runs, two lines on the order, and the heavier weight belongs to the thinner layer.
Graded numbers here, drive stone on the other page
This page is for material ordered by its number: a specification, a drawing, a trench detail, a bedding note. If what you are buying is described by where it goes rather than by a grade, the gravel calculator is the page for it, and a compacted limerock layer under a drive belongs on the limerock base calculator.
When the tonnage is settled, take it to the listing that matches the number you specified, not the one nearest to hand: #57 Limestone for drains and general work, #67 Stone around pipe, 3/4" Crushed Stone for drainage beds and construction entrances. Pick a quantity and a date on the listing, and leave the driver firm ground near the trench, because moving several tons of angular stone twice is a long afternoon.
Common questions
I am compacting the pad but not the drain. Should the 5 percent box be on for both?
Tick it for both, for different reasons. Angular stone settles when it is rolled, and loose stone going into an open trench loses material over the edges and down the wheelbarrow route. It is a small allowance either way, so on a trench you are about to bury, round the tonnage up as well.
The drain line runs from the slab down to the swale. Do I tape the fall or the flat distance?
The fall. You are filling the trench you dug along the ground, so the length is measured along it. On a gentle slope the difference is small, but a run that drops several feet over its length is measurably longer than its plan distance.
The drain turns the corner of the lanai and carries on. Is that one run of the tool?
One run, two areas. Choose Multiple areas, enter each leg as its own rectangle at the same trench width, and stop the first leg where the second starts. The corner section only gets counted once that way.
A brick edge is going around the finished stone strip. Does it count in the width?
Only if stone goes under it. Where the edge sits on its own bed, measure inside it. Where the strip is being built first and the edge set on top afterwards, measure to the outer line.
How do I keep a pad's base layer and its screenings cap as two separate orders?
Run the tool twice on the same footprint. First at the base depth with the coarse grade selected, then at the cap depth with screenings selected, and write the two tonnages down separately. Order them as separate lines so they arrive as separate piles, because mixing the cap into the base costs you both layers.
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