A gravel order goes wrong in the yard, not on the spreadsheet. You measure a drive in meters, the quarry quotes short tons, the loader operator fills by the bucket, and the load that arrives either runs out three meters short of the garage or leaves a hump of stone you have to barrow away. The five inputs on this page turn a marked out area, a compacted depth, and a bulk density taken from the delivery ticket into a mass you can read back to the supplier before the truck is loaded.
What the bulk density number really controls
Length, width, and depth give you volume. Density is the only input that turns that volume into a weight a weighbridge will agree with, and it is the input most people guess. The default of 1700 kg/m3 sits in the middle of the range quarries quote for crushed limestone and granite blends. Drop it to 1500 kg/m3 and the 1.8 cubic meter pad used further down this page falls from 3.366 tonnes to 2.970 tonnes; push it to 1900 kg/m3 and the same excavation needs 3.762 tonnes. That is a swing of almost 27 percent from one field you may have typed without thinking. NIST lists the exact factor 1.601 846 E+01 for pounds per cubic foot to kilograms per cubic meter, so a datasheet printed as 106.1 lb/ft3 is the same 1700 kg/m3 this page expects. Ask the quarry for the density of the graded product you are actually buying rather than for washed single size stone, because the two differ and only one of them is going into your trench.
Getting the four field measurements right
- Square the area before you tape it. Drive a peg at each corner and run a string line between them. Check both diagonals with a tape; on a true rectangle they should match within roughly 10 mm, and if they do not the shape is a parallelogram and your area is overstated. Record length and width in meters to two decimal places. Tool: Tape measure and string line.
- Split awkward shapes into rectangles. Very few drives are honest rectangles. Break the plan into rectangles and triangles, measure each piece separately, add the areas, then enter one length and width pair whose product matches that total. Sketch the split on paper so you can check the arithmetic later. Tool: Graph paper sketch.
- Measure depth from the compacted level. Lay a straightedge across the excavation on the finished surface line and drop a tape from its underside to the formation. Take at least four readings, one near each corner, and use the shallowest if you intend to grade the base rather than simply averaging them. Tool: Straightedge and tape.
- Take density from the quarry, not memory. Call the quarry with the exact product name and ask for the bulk density in kilograms per cubic meter for that graded product. Write the figure and the date on your sketch, because yards revise the number when they open a new face or change the blend. Tool: Quarry ticket or datasheet.
- Set waste from edges and handling. Walk the perimeter and count the places where stone will escape: open edges, soft verges, the barrow route, and the tipping point. The default of 10 percent suits an area with a fixed edging, and 15 percent is closer for open sides on sloping ground.
Depth, lifts, and what a compacted layer means
The depth field is the finished, compacted thickness, not the height of the loose heap the truck tips out. FHWA guidance on granular base spreads material in thin layers of 150 mm (6 in) to 200 mm (8 in) before compaction, which is why a deep sub base is never placed in a single pass. For unpaved running surfaces the same agency puts wearing course thickness above 4 in (100 mm) and describes a crown of 4 to 5 percent as adequate for water to flow off the road. Read the default of 0.075 m against those figures: 75 mm is a decorative path or a shallow top up, not a drive that takes a delivery truck. If you are building a 300 mm sub base under a 75 mm wearing course, run this page twice, once for each layer, because the two products carry different densities, different maximum sizes, and different prices per tonne.
| Unit on the quote | Exact factor published by NIST | Applied to the example above |
|---|---|---|
| Ton, short (2000 lb) | Multiply by 9.071 847 E+02 for kilograms | Order of 3.366 tonnes equals 3.710 short tons |
| Ton, metric (t) | Multiply by 1.0 E+03 for kilograms, exact | Order of 3.366 tonnes equals 3366 kg on the ticket |
| Cubic yard (yd3) | Multiply by 7.645 549 E-01 for cubic meters | Compacted 1.8 cubic meters equals 2.354 cubic yards |
| Inch (in) | Multiply by 2.54 E-02 for meters, exact | Depth entry of 0.075 m equals 2.953 inches |
| Square foot (ft2) | Multiply by 9.290 304 E-02 for square meters, exact | Pad of 24 square meters equals 258.33 square feet |
| Pound per cubic foot (lb/ft3) | Multiply by 1.601 846 E+01 for kg/m3 | Density of 1700 kg/m3 equals 106.1 lb/ft3 |
Source: National Institute of Standards and Technology, NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically.
Factors marked exact are exact by definition; the remaining two are quoted as NIST publishes them, rounded to seven significant figures.
Working a 24 square meter parking pad
| Field | Value |
|---|---|
| length | 8 |
| width | 3 |
| depth | 0.075 |
| density | 1700 |
| waste | 10 |
The pad is 8 m by 3 m, which is 24 square meters, or 258.33 square feet at the exact NIST factor. At a compacted depth of 0.075 m the excavation holds 1.8 cubic meters, which is 2.354 cubic yards if your supplier prices by volume. Multiply that volume by the ticket density of 1700 kg/m3 and you get 3060 kg, or 3.06 tonnes of stone actually sitting in the hole. The 10 percent waste allowance is applied last, to the mass rather than to the volume, which lifts the order to 3.366 tonnes. Read that back as 3366 kg, or 3.710 short tons if the yard prices that way. Nothing is rounded up to a whole truck load along the way, so where a supplier sells in fixed drops you still have to choose between under ordering and paying for part of a load you will not use. Depth and density enter as equal linear factors: the same percentage change in either produces the same percentage change in the result.
Result: 3.366 tonnes.
Fines content decides whether the stone locks up
Two loads that look alike on the ticket behave differently underfoot because of what passes the 0.075 mm sieve. FHWA guidance on granular base caps that fines fraction at a maximum of 8 percent, allows up to 12 percent in a granular subbase, and tightens it to 6 percent where the subbase itself has to drain without holding water. The same guidance notes that base density is maximized at a fines content between 6 and 20 percent, that load carrying capacity decreases once fines exceed about 9 percent, and that in excess of 50 percent of the coarse aggregate particles should be crushed rather than rounded. Maximum size matters as well: 50 mm (2 in) or less for granular base, against a nominal maximum size commonly up to 100 mm (4 in) for subbase. Rounded pea gravel with almost no fines never locks, so it stays loose, migrates toward the edges, and needs topping up long before the tonnage on this page would suggest.
Common mistakes
- Ordering by the ton when the calculated answer is printed in tonnes.
- A short ton is 907.18474 kg against 1000 kg for a metric tonne, so a yard quoting short tons is selling about 9.3 percent less mass for every unit you name. Convert before you telephone. The 3.366 tonne example is 3.710 short tons, and naming the wrong unit costs roughly a third of a ton even on a pad this small.
- Entering the loose delivered depth instead of the compacted depth.
- Stone bulks when it is tipped and settles when it is rolled, so a heap measuring 100 mm loose does not leave 100 mm of compacted surface once it has been worked and graded. Measure the depth you want after compaction, let the waste percentage absorb handling losses, and check the finished level with a straightedge before ordering a top up.
- Reusing one density figure for base stone and decorative gravel.
- Graded crushed material carrying fines packs far tighter than washed single size stone, so the same 1.8 cubic meter excavation runs from 2.970 tonnes at 1500 kg/m3 to 3.762 tonnes at 1900 kg/m3. Run the page once per product using the density on each datasheet, then keep the two orders on separate lines of the purchase note so the driver tips them in the right place.
- Treating a bulk tonnage as though it were a bag count.
- Bagged aggregate is sold by mass per bag while bulk stone is sold by mass or by volume, and bag counts round up in whole units that will never land exactly on a calculated tonnage. Divide the tonnage by the mass printed on the bag label, round the count upward, and compare the bagged price against a loose load before you commit to either.
Paths people walk on and when to call an engineer
A gravel path that visitors have to use is held to a different standard from a decorative bed. The ADA standards require accessible floor and ground surfaces to be stable, firm, and slip resistant, limit openings in ground surfaces so they will not pass a 1/2 inch diameter sphere, allow changes in level of up to 1/4 inch with no treatment, and require anything between 1/4 inch and 1/2 inch to be beveled at a slope no steeper than 1:2. Loose rounded stone fails every one of those tests the moment a wheel sinks into it. Where the route has to serve the public, price a bound or stabilized surface over a compacted base and use this page for the base layer only. Bring in a civil or geotechnical engineer, not a calculator, when the gravel carries vehicle loads over soft ground, sits behind a retaining wall, or forms part of a drainage run within a few meters of a foundation.
Frequently asked questions
Does the waste percentage apply to volume or to mass?
It is applied to mass, at the very end of the calculation. The page works out volume from length, width, and depth, converts that volume into kilograms using the density you entered, and only then multiplies by one plus the waste fraction. On the worked example that is 3.06 tonnes of stone in the ground and 3.366 tonnes on the order. Because the step comes last, the percentage behaves identically whether you end up buying by weight or by volume.
How deep should gravel go on a drive rather than a path?
FHWA unpaved roads guidance puts wearing course thickness above 4 in (100 mm) and describes a crown of 4 to 5 percent as adequate for water to flow off the road, while its granular base guidance spreads material in layers of 150 mm (6 in) to 200 mm (8 in). A 75 mm decorative depth, the default on this page, sits well below that. Anything carrying vehicles normally needs a separate sub base under the surface layer, which means two runs of this page with two densities.
Can I use this page when the quarry quotes cubic yards?
Yes, but convert the volume rather than the tonnage. One cubic yard is 7.645 549 E-01 cubic meters at the exact NIST factor, so the 1.8 cubic meter example is 2.354 cubic yards before waste and 2.590 cubic yards once 10 percent is added. Order in whichever unit the yard prices in, and keep the density on file regardless, because delivery notes are usually issued by weight even when the quotation was written by volume.
Why does my supplier quote a different tonnage for the same job?
Three things usually explain the gap. The yard may be applying a different bulk density to the same product name, it may be quoting loose volume rather than compacted volume, or it may be rounding up to whole truck loads. Ask which density figure was used and whether the quotation is loose or compacted; once both of you are working from the same kilograms per cubic meter, the two numbers normally close to within a few percent.
Is a loose gravel path suitable for wheelchair access?
Usually it is not. The ADA standards require accessible ground surfaces to be stable, firm, and slip resistant, restrict openings so that a 1/2 inch diameter sphere cannot pass, permit changes in level of up to 1/4 inch untreated, and require a bevel no steeper than 1:2 for anything between 1/4 inch and 1/2 inch. Meeting that in practice means a bound or stabilized surface over a compacted base, so use this page for the base layer alone.
Related calculators
Sources
- Granular Base, User Guidelines for Waste and Byproduct Materials in Pavement Construction Federal Highway Administration. Supplies the 150 mm to 200 mm spreading layers, the 8, 12, 6, 20 and 9 percent fines limits, the 50 percent crushed particle figure, and the 50 mm and 100 mm maximum sizes quoted on this page. Accessed 2026-09-07.
- Planning an Unpaved Road Improvement Program, Unpaved Road Dust Management Handbook Federal Highway Administration. Supports the statement that a crown of 4 to 5 percent sheds water and that wearing course thickness should be greater than 4 in (100 mm), which is how the 75 mm default is judged here. Accessed 2026-09-07.
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically National Institute of Standards and Technology. Provides every factor in the conversion table, including 9.071 847 E+02 for the short ton, 7.645 549 E-01 for the cubic yard, and 1.601 846 E+01 for pounds per cubic foot. Accessed 2026-09-07.
- Guide to the ADA Standards, Chapter 3: Floor and Ground Surfaces United States Access Board. Backs the stable, firm, and slip resistant requirement, the 1/2 inch sphere limit on openings, and the 1/4 inch and 1/2 inch change in level rules with the 1:2 bevel used in the path section. Accessed 2026-09-07.
This is a planning result, not a supplier quote; sellers use different pack, bag, board, roll, and bundle conventions, so confirm the exact product label and selling unit before you order.