Gravel Base Calculator

Four inches of compacted base under a paver patio, walkway or shed floor. Six inches under a driveway carrying cars. Eight to twelve inches if the subgrade is soft clay or you see tyre ruts forming while you work — in that case a geotextile separation fabric is worth adding too.

Crusher run or road base — angular crushed stone that still contains its fines. The fines fill the voids so the layer compacts into something solid. Clean single-sized gravel drains beautifully but will not compact, and rounded river rock is useless as a base.

Expect to lose 15 to 20% of the loose depth. So for a finished 4 inch compacted base, spread close to 5 inches loose. The calculator's default 20% allowance already accounts for this.

Measure the length and width in feet at the widest points and multiply them. For an irregular bed, break it into rectangles, circles and triangles, calculate each one separately and add the results together. Rounding up slightly is safer than rounding down.

Bulk is almost always cheaper per cubic yard once you need more than about 1 cubic yard — roughly 54 bags. Bags win when you need a small amount, have nowhere to dump a pile, or want to spread the job over several weekends.

A half-ton pickup can usually carry about 1 cubic yard of light material like mulch, but only around half a cubic yard of wet soil or gravel because of the weight. Check the weight figure above against your vehicle's payload rating before you load up.