What is ProMaterialCalc?

A precise concrete and slab volume estimator designed for contractors and DIYers to calculate material requirements, bag counts, and waste margins instantly.

Are these calculators free to use?

Yes. Every estimator on ProMaterialCalc is free, with no account, no sign-up, and no limit on how often you use it. The dimensions you type stay in your browser, so nothing about your project is stored on our servers.

How accurate are these estimates?

The maths follows the same steps as a quantity takeoff, using published bag yields (about 0.6 cubic feet for an 80 lb bag of concrete mix, 0.45 cubic feet for a 60 lb bag) and standard bulk densities for aggregate. That makes a result reliable to within a bag or a fraction of a cubic yard, which is as accurate as the dimensions you feed it. Confirm the final figure with your supplier before ordering, because stock, moisture content, and bag labels can shift the last few percent.

What waste factor should I add?

5 to 10 percent for concrete poured into a form, 10 percent for a standard rectangular mulch bed, 15 percent for curved, island, or sloped beds and for any 4 inch layer, and around 10 percent for gravel so the sub-base still compacts to full depth. Running short of concrete is expensive and unforgiving, so round up rather than down.

How much concrete do I need for a slab?

Multiply length by width by depth in feet to get cubic feet, then divide by 27 for cubic yards. A 10ft x 10ft slab at 4 inches deep is 100 sq ft x 0.333ft, or 33.3 cubic feet, which is 1.23 cubic yards. Add a 10 percent buffer and you would order about 1.36 cubic yards.

How many bags of concrete are in a cubic yard?

About 45 bags of the 80 lb mix, or 60 bags of the lighter 60 lb mix, because one 80 lb bag yields roughly 0.6 cubic feet and one 60 lb bag roughly 0.45 cubic feet. A cubic yard of mixed concrete weighs close to 4,000 lb, so once a pour passes about 60 bags most people switch to ready-mix delivery.

How thick should a concrete slab be?

4 inches is the standard for patios, walkways, shed floors, and garden paths over a compacted base. Driveways, garage slabs, and anything else carrying vehicle weight are usually 5 to 6 inches with reinforcement. Structural work, frost-exposed slabs, and anything that needs a permit should take its depth from your local code or a licensed engineer, not from a default.

How much mulch do I need per acre?

One acre is 43,560 square feet. At the standard 3 inch depth that is about 403 cubic yards, which is roughly 10,890 cubic feet; at 2 inches it is about 269 cubic yards, and at 1 inch about 134 cubic yards. In the common 2 cu. ft. bags, a 3 inch application over a full acre would take around 5,445 bags, which is why acre-scale jobs are always ordered in bulk by the yard and spread over several deliveries.

What is the best mulch thickness for a driveway?

Mulch is not a driveway surface: it breaks down, blows and washes away, and will not carry a vehicle, so no mulch depth makes a driveway work. If you are adding mulch to a planted strip or border alongside a driveway, 2 to 3 inches is right, feathered to about 1 inch at the edge so it does not spill onto the paving. If you mean the driveway surface itself, that job takes crushed stone at 4 to 6 inches, compacted in lifts, and the gravel estimator covers it.

How thick should mulch be in garden beds?

2 to 3 inches is the standard refresh for established flower, shrub, and perennial beds. New beds and areas with heavy weed pressure can go to 3 or 4 inches, but do not go deeper over living roots, and keep all material 1 to 2 inches clear of trunks and stems. Topdressing a lawn or covering grass seed takes only 1 to 2 inches.

How many bags of mulch are in a cubic yard?

About 14 bags of the common 2 cu. ft. size, 9 bags of the larger 3 cu. ft. size, or 27 small 1 cu. ft. bags. Bagged mulch is compressed for shipping, so a bag's stated volume is the settled volume you are paying for. Once a project passes roughly 10 to 15 bags, bulk delivery by the cubic yard is usually cheaper per unit and far less work.

How much mulch do I need for a 10ft x 20ft bed?

A 200 sq ft bed takes 50 cubic feet at 3 inches deep, which is 1.85 cubic yards, or about 25 bags of 2 cu. ft. mulch. With the standard 10 percent landscaping buffer that becomes 55 cubic feet, or 2.04 cubic yards.

How often do I need to top up mulch?

Organic mulch settles and decomposes, so plan on 1 to 2 inches a year after the first installation. If the existing layer has matted into a crust more than about 2 inches thick, break it up with a rake before adding more, and keep the total depth under 4 inches so water and air still reach the roots.

Is topsoil the same as mulch?

No, and mixing them up is a common and costly mistake. Mulch is a surface layer chosen to suppress weeds, hold moisture, and look tidy. Topsoil is a growing medium: it is what goes down under sod, seed, or new plantings so roots have something to establish in. A new bed usually wants 4 to 6 inches of topsoil first, then a 2 to 3 inch mulch layer on top.

How deep should a gravel driveway be?

4 to 6 inches of compacted crushed stone over prepared, graded ground is the usual specification for a residential driveway, laid in two lifts and compacted between them. Where the ground is soft or regular heavy loads cross it, go to 6 inches with a geotextile fabric underneath. A decorative top layer, if you want one, adds a further 2 to 3 inches.

How many tons are in a cubic yard of gravel?

Crushed stone runs about 1.35 tons per cubic yard at a bulk density near 2,700 lb per cubic yard. Pea gravel is slightly lighter at about 1.30 tons, sand and stone dust heavier at about 1.40 tons, and river rock lighter again at about 1.25 tons. Tonnage is what limits the delivery truck rather than volume, so keep both numbers ready when you call.

How many 50 lb bags of gravel make a cubic yard?

Crushed stone at roughly 2,700 lb per cubic yard works out to about 54 bags of 50 lb, which is around 1.35 tons. Anything beyond a small repair is cheaper and much faster ordered in bulk by the yard or by the ton.

FAQ

Frequently asked questions

The questions we get most about estimating concrete, mulch, topsoil, and aggregate, with the numbers behind each answer: bag yields, bag counts per cubic yard, material densities, and the depths crews actually install.

Using the calculators Concrete questions Mulch & topsoil questions Gravel & driveway questions

Using the calculators

Concrete questions

Mulch & topsoil questions

Gravel & driveway questions

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