Gravel calculator
For the compacted gravel or crushed stone base under a slab, driveway, patio or shed. Enter the area and the finished depth to get cubic yards, then add your supplier’s weight per yard to get tons.
Calculator
Gravel to order
Enter your measurements and select Calculate gravel.
- Loose gravel to order
- cu yd
- Compacted volume
- cu yd / cu ft
- Weight
Length × width × depth in feet gives cubic feet. Divide by 27 for cubic yards, then add the extra for compaction.
How the gravel calculator works
The base under concrete is a flat layer, so its volume is length times width times depth, with depth converted from inches to feet. That gives the compacted volume: the space the finished base fills. Loose stone takes up more room than compacted stone, so the calculator adds a percentage for compaction and spillage, then converts to cubic yards and, if you enter a weight, to tons.
Compacted volume (cu yd) = length (ft) × width (ft) × depth (in) ÷ 12 ÷ 27
Loose gravel to order = compacted volume × (1 + extra %)
Tons = cubic yards to order × your supplier’s tons per cubic yard
Worked example
A 20 × 10 ft shed base with 4 in of compacted crushed stone, 15% extra, and a quarry that quotes 1.5 tons per cubic yard:
- Volume: 20 × 10 × (4 ÷ 12) = 66.67 cu ft = 2.47 cu yd compacted
- Loose to order: 2.47 × 1.15 = 2.84 cu yd
- Weight: 2.84 × 1.5 = 4.26 tons
Why we ask for the weight
Gravel and crushed stone are usually sold by the ton, but the weight of a cubic yard depends on the stone type, particle size, how much fine material it contains and how wet it is. Published figures for crushed stone generally fall between about 1.4 and 1.7 tons per cubic yard, but your quarry’s number is the one that matters for your order and your bill. Ask for it, or read it from their product page, and enter it here.
What to enter
- Length and width. The base usually extends a few inches beyond the slab on each side. Measure the base, not the slab.
- Compacted depth. The finished thickness after tamping. Four inches is common under patios and shed slabs; driveways often use more, and poorly draining soil may need more still. Check local practice or your plans.
- Extra for compaction. Crushed stone compacts noticeably. Suppliers often suggest ordering 10 to 20% more loose material than the compacted volume; 15% is the default here. Clean rounded gravel compacts less than crusher run with fines.
- Weight per cubic yard. From your supplier. Leave blank to see cubic yards only.
Limitations
- This is a material estimate. Base depth and the type of stone to use depend on soil, drainage and load, and should follow your plans or local practice.
- Trucks deliver in whole loads. A small order may be charged at a minimum quantity.
- The calculator does not subtract the slab’s own thickness or include sand bedding, geotextile fabric or edge restraint.
Frequently asked questions
How much gravel do I need under a concrete slab?
A 4 in compacted base is common under residential slabs. For a 12 × 12 ft slab that is 12 × 12 × 0.333 = 48 cu ft, or 1.78 cu yd compacted. Order about 2 cu yd loose to allow for compaction.
How many tons is a yard of gravel?
It depends on the product. Crushed stone is often quoted between about 1.4 and 1.7 tons per cubic yard, with road base containing fines at the heavier end. Your supplier’s figure is the one to use.
What size gravel goes under concrete?
Crushed stone that compacts well, such as a 3/4 in crushed aggregate or a road-base blend with fines, is the usual choice. Rounded pea gravel does not lock together and is a poor base. Ask your supplier what local contractors use under slabs.