How it is calculated
Area times depth gives the volume; an allowance is added because loose material settles when it is compacted and some is lost on delivery. Weight is the volume times the bulk density. Densities of dry, loose material are from Engineering ToolBox: sand 97 lb/ft³ (1,555 kg/m³), gravel 105 lb/ft³ (1,680 kg/m³), sand with gravel 108 lb/ft³, loose dirt 78 lb/ft³. If your supplier quotes a figure, choose “Supplier’s density”.
Volume = L × W × h × (1 + allowance)Weight = volume × bulk densityBags = weight ÷ bag weight, rounded upExample
An area of 20 × 10 ft at 4 in deep with a 10% compaction allowance needs about 2.7 cubic yards. In gravel that is about 3.8 tons, or 154 bags of 50 lb.
Tips from practice
- Sand and gravel are sold by the cubic metre or by the tonne — ask which the price is for.
- Lay a sub-base in layers of 10–15 cm and compact each one.
- Wet sand weighs about a fifth more than dry sand.
Questions and answers
How much does a cubic yard of gravel weigh?
About 1.4 tons (2,835 lb) of dry gravel at 105 lb/ft³; damp or crushed rock can be heavier.
How much does a cubic yard of sand weigh?
Dry, loose sand is about 1.3 tons (2,620 lb) per cubic yard; damp sand around 1.6 tons.
How much should I allow for compaction?
For a gravel or sand base, typically 10–20%.
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