About this tool
This driveway concrete calculator sizes the whole job, not just the concrete. Enter the driveway's length, width, and thickness, add the flared apron where it meets the street, and choose a waste allowance; the page returns the volume in cubic feet, cubic yards rounded up to the quarter yard a ready-mix plant will bill, and the equivalent count of 40, 60, and 80 lb bags. It then estimates the reinforcement, either #3 or #4 rebar on a 12, 18, or 24 inch grid or 6x6 welded wire mesh sheets, and the compacted gravel base under the slab in cubic yards and tons. Prices per yard, per bag, per ton, and per rebar stick turn it into a material budget. It is for homeowners comparing quotes, DIY pourers ordering a truck, and anyone deciding between 4 and 6 inch thickness.
How it works
Slab area = length x width plus the apron flare, modeled as two right triangles (2 x 1/2 x flare width x flare length). Volume in cubic feet = area x thickness in inches / 12, then x (1 + waste%); cubic yards = cubic feet / 27, rounded up to the next 1/4 yard for ordering. Bags use the standard premix yields of 0.30, 0.45, and 0.60 cubic feet for 40, 60, and 80 lb bags. Rebar: bars running lengthwise = floor(width in inches / spacing) + 1, each the slab length; bars across = floor(length in inches / spacing) + 1, each the slab width; total feet x 1.10 for overlaps / 20 ft sticks, with weight at 0.376 lb/ft for #3 and 0.668 lb/ft for #4. Mesh: 5 x 10 ft sheets covering about 45 sq ft each after a 6 inch overlap. Gravel base: area x base depth / 12 cubic feet, converted to yards and to tons at 105 lb per cubic foot for compacted crusher run.
Frequently asked questions
How thick should a concrete driveway be?
Four inches is the residential standard for cars and light trucks over a compacted 4 inch gravel base. Go to 5 or 6 inches where delivery trucks, RVs, boats on trailers, or garbage trucks will drive or park, and at the apron where vehicles turn. Each extra inch adds 25 percent to the concrete volume of a 4 inch slab, so a 6 inch driveway costs about 50 percent more in concrete but lasts much longer under heavy loads. Control joints should be cut every 8 to 12 feet either way.
Do I need rebar or wire mesh in a driveway?
Reinforcement does not stop concrete from cracking, but it holds the cracks tight so the slab stays level. For a 4 inch residential driveway, 6x6 W1.4 welded wire mesh or #3 rebar on an 18 inch grid is common; #4 rebar on 12 to 18 inches is used for 5 to 6 inch slabs and heavy loads. The steel must sit in the middle of the slab on chairs or dobies, not on the gravel, or it does nothing. Fiber-reinforced mix helps with surface shrinkage cracks but is not a substitute for steel across joints and aprons.
How much gravel base goes under a driveway?
A compacted base of 4 inches of crusher run or 3/4 inch minus road base is typical on well-drained soil, and 6 to 8 inches on clay or where frost heave is a problem. The calculator uses area x base depth and converts to cubic yards and tons at about 1.4 tons per loose cubic yard. Order 10 to 15 percent extra because base rock compacts and some is lost leveling the subgrade. Never pour on topsoil or uncompacted fill.
Is it cheaper to use bags or a ready-mix truck?
For anything over about 1 cubic yard, ready-mix wins on both cost and quality: a 6.75 yard driveway is roughly 300 bags of 80 lb mix, which is a full day of mixing and 24,000 lb to haul. Ready-mix arrives at a consistent strength and slump and is placed in an hour or two. Expect a short-load fee under 4 to 6 yards and a per-yard price that varies widely by region; enter your quote in the cost field to compare.