How much gravel do I need?
The amount of gravel for a job is a volume, and a volume is an area multiplied by a depth. Measure the surface you want to cover, decide how deep the layer should be, and the rest is unit conversion. A garden path, a driveway, a drainage trench and a patio base all follow the same sequence: area, depth, volume, weight, and then the way your supplier sells it, whether that is bulk by the cubic yard, by the tonne or in bags. This calculator keeps each stage visible in a ledger, so you can see where every number comes from and change one assumption at a time.
Three decisions matter more than any formula. The first is depth, which depends on the use and on your supplier's guidance rather than on this page. The second is density, because the weight of a cubic yard changes with the material, its moisture and how it is graded. The third is the allowance. Ground is rarely perfectly level and loose stone settles, so many people order slightly more than the measured volume. Enter your own percentage; the calculator shows the measured volume and the order volume on separate lines so the extra is never hidden.
Area and depth to volume
For a rectangle, multiply length by width to get the area, then multiply by the depth. Every length must be in the same unit before you multiply, which is why the calculator converts each entry to metres first. A 10 m by 5 m area covered to a depth of 5 cm is 10 × 5 × 0.05 = 2.5 cubic metres. For a circular bed, the area is π times the diameter squared, divided by four. A circle ten feet across and three inches deep needs 19.63 cubic feet, which is 0.727 cubic yards.
If you already know the area, for example from a plan or from the square footage calculator, choose the total area option and enter it directly. If you know the volume, perhaps from a drawing, choose the volume option and skip the depth. Irregular spaces are easiest to handle by splitting them into several sections. A 6 m by 3 m bed at 10 cm deep holds 1.8 cubic metres; adding a 2 m round feature at the same depth brings the total to 2.114. The calculator sums the sections first and rounds only once at the end, so a long list of small areas does not pile up rounding error.
The calculator accepts millimetres, centimetres, metres, inches, feet and yards for lengths, and square feet, square yards, square metres and acres for areas. Mixing units in one job is fine, because each entry is converted separately. A quantity box repeats an identical section, such as four matching planting strips, without you typing the same dimensions again.
Volume to tons and density
Gravel is bought by weight far more often than by volume, so the next step is density, the weight of one cubic unit. Multiply the order volume by the density and you have the order weight. The calculator takes density in kilograms per cubic metre, pounds per cubic foot or US short tons per cubic yard, and it converts between them using exact definitions: one pound is 0.45359237 kilograms and one US short ton is 2,000 pounds. Nothing is assumed about the type of stone. The starting figure of 1,680 kg/m³ is only an example, and you should replace it with the number on your supplier's data sheet or delivery ticket.
That sensitivity is why there is no table of materials here. Two loads of the same stone can weigh different amounts if one is wet, and a finer grading packs more tightly than a coarse one. A 5% difference in density is a 5% difference in the number of tons you pay for, so the supplier's own figure is worth the phone call.
US tons versus metric tonnes
Two different units both get called tons. A US short ton is 2,000 pounds, about 907.18 kilograms. A metric tonne is exactly 1,000 kilograms, and a UK long ton is a third unit that this calculator does not use. The results show US short tons and metric tonnes side by side, with the unit spelled out each time, so you can compare a quote in one unit with a delivery ticket in another. As a check, the driveway example below weighs 8.3 US short tons, which is 7.53 metric tonnes.
Bags and order allowance
Bagged gravel is counted in whole bags, so the bag count is always rounded up, and it is rounded only once, after all sections are added. Enter what one bag holds, either by weight or by volume. The calculator then divides the matching order quantity by the bag size. It never guesses the volume of a bag from its weight, because that would need a density the bag label may not give. With the 2.75 cubic metres from a 10% allowance on the first example at 1,600 kg/m³, the order weighs 4,400 kg, which is 176 bags of 25 kg. The leftover is shown too, so you can see whether a larger bag would waste less.
The allowance deserves a line of its own. It is a planning assumption, not a measurement. A 10% allowance on 2.5 cubic metres adds 0.25 cubic metres, which turns 2.5 into 2.75. Compare that with the 5% used for the garden bed, where 1.8 becomes 1.89 cubic metres. You may want more for a soft base, a sloping site or a thin layer spread over rough ground, and less for a flat, firm, well-measured surface. Zero is a valid allowance if you want the exact measured quantity.
Small areas show how bag counts behave. A 3 m by 2 m strip at 5 cm deep needs 0.3 cubic metres, or 10.59 cubic feet. In half-cubic-foot bags that is 22 bags, and the last one is only partly used.
Material and delivery costs
Prices are optional and always your own figures; the calculator does not look anything up. Enter a bulk price and choose what it is per, whether cubic yard, cubic metre, cubic foot, litre, metric tonne, US short ton, kilogram or pound. The bulk cost is the price multiplied by the order quantity in that unit. A bag price is multiplied by the whole number of bags. A single delivery charge, if you enter one, is added once to each total and is never multiplied by loads or bags.
In the worked case with a bulk price of 30 per cubic metre, the material for 2.75 cubic metres costs 82.50. The same order bought as 176 bags at 2 each costs 352.00. Put your own prices in to see the gap. The comparison is only about material: labour, hire of a compactor, geotextile, edging and disposal of what you dig out are not included, and neither is tax unless you add it to the prices yourself. For an item-by-item comparison of unit prices across pack sizes, the unit price calculator is a handy companion.
Metric and driveway examples
A US-style driveway shows the imperial workflow. A strip 40 feet long and 12 feet wide at a depth of 4 inches is 480 square feet and 160 cubic feet, which is 5.926 cubic yards. At an example density of 1.4 US tons per cubic yard that weighs 8.3 tons. Adding a 10% allowance raises the order to 6.519 cubic yards and 9.13 tons.
A metric garden bed shows the other route. Six metres by three metres at 10 cm is 1.8 cubic metres. At 1,680 kg/m³ the weight is 3,024 kg, or 3.024 metric tonnes, and with a 5% allowance it is 3,175 kg. Both examples were computed by the calculator above with the stated inputs, so you can reproduce them by typing the numbers in.
| Job | Order volume | Order weight |
|---|---|---|
| 10 m × 5 m × 5 cm at 1,600 kg/m³ | 2.5 m³ | 4,000 kg |
| 40 ft × 12 ft × 4 in at 1.4 tons/yd³ | 5.926 yd³ | 8.3 US tons |
| Circle 10 ft across × 3 in at 1.4 tons/yd³ | 0.727 yd³ | 1.02 US tons |
| 6 m × 3 m × 10 cm at 1,680 kg/m³ | 1.8 m³ | 3,024 kg |
If the gravel sits under or around other work, estimate that work separately. The concrete calculator handles slabs, footings and posts, so you can estimate a gravel base separately from the concrete that goes on top of it.
Assumptions and limits
This tool does arithmetic on the numbers you enter. It does not design a base, check drainage, judge whether a depth is suitable or promise that a supplier has a material in stock. Compaction reduces the volume of loose material, and the amount depends on the stone, the equipment and the moisture, so the allowance is yours to set. The calculator also does not model slopes, steps or voids, and it treats each section as a flat layer of constant depth. Quantities are limited to sensible sizes, and a blank field is treated as missing rather than as zero, so an empty depth cannot quietly shrink your order to nothing. Use the result as a planning figure and confirm it with your supplier before you buy.
Gravel calculator questions
How much gravel do I need?
Multiply the area by the depth to get the volume, then add the allowance you choose. For 10 m by 5 m at 5 cm that is 2.5 cubic metres, or 2.75 with a 10% allowance.
How many tons are in a cubic yard of gravel?
It depends on the density and on which ton you mean. Multiply the density by one cubic yard and divide by the weight of a ton. At the example figure of 1.4 US tons per cubic yard, 5.926 cubic yards weighs 8.3 US short tons.
Does pea gravel always weigh the same?
No. Weight depends on grading, moisture and how the load was handled, so use the density printed by your supplier rather than a general figure.
How many bags of gravel do I need?
Divide the order quantity by what one bag holds and round up once. Using a bag size in the same kind of unit as your order, such as kilograms for weight, keeps the result reliable. 4,400 kg in 25 kg bags is 176 bags.
Does the cost include delivery?
Only if you enter a delivery charge. It is added once to the bulk total and once to the bag total, and it is not multiplied. Labour and other materials are not included.