Gravel Base Calculator

1. Enter the length and width of the base area in feet.
2. Enter the compacted depth in inches, the finished depth after the base is compacted.
3. Pick the material, or choose Custom density and type in the compacted weight per cubic yard from your supplier.
4. Set a waste allowance for spillage and grading, then read the tons and the loose cubic yards.

Here is what each result line means:

A gravel base calculator turns the size of a patio, driveway, walkway or pad into the amount of crushed stone or sand to order for the layer underneath it. You give it the area and the compacted depth, and it returns a weight in tons and a volume in cubic yards.

The tricky part with aggregate is that the same weight of stone takes up different amounts of room depending on how tightly it is packed. A base is specified by its compacted depth, but stone arrives loose. This tool works from the compacted weight per cubic yard, so the tons it gives fill your depth once the base is compacted, and it also shows the larger loose volume you will see in the truck or the pile.

A base sits under many kinds of flatwork. For the concrete on top of a garage slab, the garage floor calculator sizes the pour; for a spa slab, the hot tub pad calculator does the same. Interlocking pavers also sit on a compacted aggregate base, as the ICPI construction tolerance guide shows.

The base is a flat block of material, so its volume is length times width times depth. Because the depth is in inches and the plan area is in feet, the tool divides by 12 to get cubic feet, then by 27 to get cubic yards.

To turn volume into an ordering weight, the compacted cubic yards are multiplied by the compacted weight per cubic yard for the material you choose and divided by 2,000 pounds per short ton. The waste allowance is added last.

1. Multiply length by width for the base area in square feet.
2. Multiply by the compacted depth in inches and divide by 12 for cubic feet, then by 27 for cubic yards.
3. Multiply by the compacted density and divide by 2,000 for tons, then add the waste allowance.
4. Divide the total weight by the loose density for the loose cubic yards to haul.
5. Separately, depth divided by 36 times the compacted density gives pounds per square yard, the way the source table is laid out.

The same arithmetic works for concrete. If you want the weight of the slab that will sit on this base, the concrete weight calculator gives it.

Suppose a 20 by 20 foot patio gets a base of crushed granite or limestone compacted to 4 inches, with the default 10 percent allowance. The tool uses 3,180 pounds per compacted cubic yard and 2,500 pounds per loose cubic yard for that material.

Calculation: the area is 20 x 20 = 400 sq ft. At 4 inches deep, 400 x 4 / 12 = 133.33 cu ft, and 133.33 / 27 = 4.938 cu yd compacted. Multiplied by 3,180 pounds that is about 15,704 pounds, or 7.85 tons. Adding 10 percent gives 8.64 tons.

The compacted volume with waste is 4.938 x 1.10 = 5.43 cu yd. Measured loose, the same 8.64 tons is 8.64 x 2,000 / 2,500 = 6.91 cu yd, which is the amount of room it takes in the truck or the pile.

As a cross-check, the pounds per square yard are 4 / 36 x 3,180 = 353.3 lb. The patio is 400 / 9 = 44.44 square yards, and 44.44 x 353.3 is again about 15,704 pounds before waste, the same answer by the table route.

The lesson: a modest patio base is already more than eight tons, and the loose yardage is noticeably larger than the compacted yardage, so order by weight and plan the delivery for the loose volume.

The Michigan LTAP highway maintenance tables, hosted by MoDOT, list several weights for each material in both a compacted and a loose state. The last column shows the pair of values this tool uses for each material.

Because the source gives a range rather than one figure, the weight of the product you actually buy can sit anywhere across it, or outside it. If your supplier quotes a compacted density for their material, choose Custom density and enter it.

Area

Tonnage rises in step with the area. Doubling the length or the width doubles the material, so measure the full footprint of the base, not just the slab or pavers on top if the plan carries the base further.

Compacted Depth

Depth multiplies the whole area. Going from 4 to 6 inches adds half as much material again, which on a driveway-sized area can be several tons. The depth comes from your plans, engineer or supplier, not from this tool.

Material and Density

Heavier stone weighs more per cubic yard. With the values used here, a compacted cubic yard of trap rock is 3,420 pounds against 3,180 for granite or limestone and 2,950 for sand, so the same base in trap rock needs more tons.

Compaction

Loose material packs down when it is compacted. The loose volume needed to reach your compacted depth is larger than the depth alone suggests, which matters for truck space and stockpiles.

Waste and Grading

Spillage, material pushed past the edges and small low spots in the subgrade all use extra. The waste allowance covers that; set it to suit your site.

Compacting a base squeezes air out of it but does not change its weight. The same tons simply occupy less room, which is why the loose volume to haul is always larger than the compacted volume in this tool.

Since the weight is the same both ways, loose cubic yards = compacted cubic yards x compacted density / loose density. For granite or limestone that ratio is 3,180 / 2,500 = 1.272, so the loose volume is about 27 percent more than the compacted volume. Trap rock is almost the same at 3,420 / 2,690 = 1.271. Sand changes much less, at 2,950 / 2,740 = 1.077, or about 8 percent. In the patio example, 5.43 compacted cubic yards x 1.272 = 6.91 loose cubic yards.

Ordering a Base for a Patio or Walkway

Size the stone under a concrete patio, a paver patio or a path before you call the supplier, so one delivery covers the job.

Building Up a Driveway

A driveway base covers a large area, so the tons climb quickly. The tool shows the tons and the loose yardage, which are the figures to discuss with the supplier when you plan the delivery.

Preparing a Shed or Equipment Pad

A small pad under a shed, a hot tub or an equipment slab is quick to size before you order, and the presets include a 12 by 10 foot shed pad to start from.

Comparing Materials

Switch between granite or limestone, trap rock and sand to see how the tonnage moves for the same area and depth.

Checking a Quote

If a contractor or supplier quotes a tonnage, enter the area and depth to see whether the figure is in the right range for the material named.

1. Ordering Compacted Yards as If They Were Loose

A base depth is a compacted depth. Ordering the compacted cubic yards by volume, as loose material, leaves you short once the base is compacted. Order by weight, or use the loose volume.

2. Measuring Depth Before Compaction

Raking out 4 inches of loose stone does not give a 4 inch base. Enter the finished, compacted depth the plan calls for.

3. Assuming Every Stone Weighs the Same

Trap rock, granite or limestone and sand all weigh different amounts per cubic yard. Pick the matching material, or enter the supplier density.

4. Skipping the Waste Allowance

Material spills off the edges and fills low spots in the subgrade. Running short means a second delivery, so keep an allowance.

5. Treating the Estimate as a Base Design

This tool does not choose the depth, the gradation or the compaction method. Those come from your plans, an engineer, the supplier or the product maker.

The arithmetic is exact for a rectangular area at an even depth; the usefulness depends on the depth and density you use.

Multiply the length by the width in feet, then by the compacted depth in inches, and divide by 12 for cubic feet and by 27 for cubic yards. Multiply by the compacted weight per cubic yard and divide by 2,000 for tons, then add a waste allowance.

At 4 inches compacted in crushed granite or limestone, a 20 by 20 foot base is about 7.85 tons net, or 8.64 tons with a 10 percent allowance, using 3,180 pounds per compacted cubic yard. A deeper base or heavier stone needs more.

It depends on the stone and how tightly it is packed. The Michigan LTAP tables list compacted crushed granite or limestone at 3,060 to 3,300 pounds per cubic yard and loose at 2,410 to 2,590. Compacted trap rock runs heavier, at 3,300 to 3,540, and compacted sand ranges from 2,830 to 3,180.

Compaction squeezes air out without changing the weight, so the same tons take less room once compacted. For granite or limestone with the values used here, the loose volume is about 27 percent more than the compacted volume.

This tool does not set the depth. Base depth depends on the load, the soil and the surface on top, and it should come from your plans, an engineer, the supplier or the product maker. Enter that depth here to size the order.

It is how much base material each square yard holds at your depth, the way the source highway tables are laid out. Multiply it by the area in square yards for the total weight, or use it to check a spread rate.

Yes. Choose Custom density and enter the compacted weight per cubic yard your supplier gives for the product. The tonnage then follows that figure. The loose volume is hidden because the tool has no loose density for a custom material.

Yes. Pick Sand to use 2,950 pounds per compacted cubic yard and 2,740 loose. Sand changes volume much less than crushed stone between loose and compacted, about 8 percent with these values.

The default is 10 percent for spillage and grading at the edges. It is a starting point rather than a rule, so raise it for an uneven subgrade or a tricky site, or lower it if your supplier advises.

Interlocking pavers sit on a compacted aggregate base, as the ICPI construction tolerance guide shows. The thickness of that base and the layers above it come from your plans, the paver maker or ICPI guidance.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Highway Maintenance Tables and Conversion Factors (Michigan LTAP tables, hosted by MoDOT; compacted and loose aggregate weights per cubic yard and the pounds per square yard formula).
• ICPI Construction Tolerance Guide (Interlocking Concrete Pavement Institute; compacted aggregate base under interlocking pavement).
• American Cement Association (American Cement Association; concrete flatwork basics).