Gravel Calculator

Background.

Ring a quarry for driveway stone and the first question back is usually how many tons. A landscape yard will ask how many yards, and at the garden centre the gravel sits in half-cubic-foot bags. What you actually know is the size of the patch, say a 40 × 10 ft parking pad, and how deep you want the stone, say 4 inches.

Getting from one to the other takes two conversions and one judgement. The geometry is fixed: 400 square feet at a third of a foot deep is 133.33 cubic feet, and a cubic yard holds 27 cubic feet. The judgement is the allowance, the extra stone that covers an uneven base, spreading losses and the settling that happens once gravel is compacted or driven on. With 8% added, the pad needs 5.33 cubic yards. Weight then depends on the stone itself. At 1.4 tons per cubic yard the order comes to about 7.47 tons, but a heavier rock, or the same rock delivered wet after rain, weighs more for the same volume.

Yards, tons and a bag count all come out of one set of measurements, so a bulk quote and a trip to the store can be compared side by side. The bag figure for that pad is 288, which settles the question for most people. Add a price per yard, per ton or per bag, whichever your supplier uses, and you get the cost of the stone. Delivery, tax, landscape fabric and edging sit outside that figure.

What is gravel calculator?

Gravel is a loose word for several quite different materials. Crushed stone is quarried rock broken into angular pieces that lock together when compacted. Washed or clean stone has had the fine particles rinsed out, so water drains through it freely. Pea gravel is small, rounded and smooth, comfortable underfoot but prone to shifting. Crusher run, or dense-graded base, mixes stone with fines that fill the gaps and compact into a firm layer. For road and bridge work, aggregate is graded by size numbers under ASTM D448, and many suppliers sell by them: No. 57 stone, for example, runs from 1 inch down to about 3/16 inch. The link between the volume you need and the weight you are sold is bulk density, the weight of a given volume of loose stone with its air gaps included. Solid granite or limestone weighs around 2.6 to 2.7 tonnes per cubic metre; the 1.4 tons per cubic yard used as the default here is about 1.66 tonnes per cubic metre, which means a loose pile of stone is more than a third air.

How to use this calculator.

1. 01Area length and area width: measure the patch in feet. For an L-shaped path, split it into rectangles and run each one; for a circle or an odd shape, work out the area in square feet, enter it as the length and enter 1 as the width.
2. 02Gravel depth: the finished thickness in inches. For a driveway with a base course and a different top stone, run each layer separately, since the materials and prices usually differ.
3. 03Waste or compaction allowance: 8% is the starting value. Raise it for a rough or soft base, or for crusher run you will compact with a plate compactor; lower it for decorative stone raked over a level, firm bed.
4. 04Bulk density: the weight of a cubic yard of your chosen material, in tons, from the supplier. If you are buying by volume, the default 1.4 does no harm, because density only affects the tons and the cost by the ton.
5. 05Bag volume, price unit and price: bag volume is printed on the bag, and 0.5 cu ft is a common size. Choose per cubic yard, per ton or per bag to match the quote you have, then enter the price in dollars.

The formula.

Cubic yards = L × W × D × (1 + a) ÷ 27, where D is the depth in feet, the inches you enter divided by 12. Length times width is the area in square feet, and multiplying by the depth gives a volume in cubic feet, and that bare figure is what the cubic-feet result shows: the volume of the space being filled, with nothing added. The allowance a (8% entered as 0.08) is applied next, and the allowance-adjusted volume feeds everything else. Dividing it by 27, the number of cubic feet in a cubic yard 3 ft on each side, gives the yards to order. Multiplying the yards by the bulk density gives tons. Dividing the adjusted cubic feet by the bag volume and rounding up to a whole bag gives the bag count. The cost uses whichever unit you price by: yards times price per yard, tons times price per ton, or whole bags times price per bag. Rearranged, the geometry yields a handy rule of thumb: a cubic yard covers 27 ÷ D square feet, which is 81 sq ft at 4 inches deep. Depth is the input to measure most carefully, since each inch on a 400 sq ft pad is about 1.23 cubic yards before the allowance. Density enters as one number for the whole order, which suits a single material but means a layered job needs one run per layer, and nothing in the arithmetic models how far a loose layer shrinks under a compactor; that loss is left to the allowance.

A worked example.

Frequently asked questions.

References& sources.

1. [1]ASTM International (2022). "ASTM D448-12(2022): Standard Classification for Sizes of Aggregate for Road and Bridge Construction." ASTM.
2. [2]Federal Highway Administration (2016). "Application Description: Granular Base." FHWA-RD-97-148.
3. [3]Federal Highway Administration (2024). "Field Materials Manual." U.S. Department of Transportation.
4. [4]U.S. Geological Survey (2026). "Mineral Commodity Summaries." National Minerals Information Center.
5. [5]National Institute of Standards and Technology (2026). "NIST Handbook 133, Appendix E: General Tables of Units of Measurement." U.S. Department of Commerce.