Ordering too little material means a second delivery fee. Ordering too much wastes money. Most quantity calculators return one number and hide how they got it, so you cannot tell whether it matches what your supplier sells. Materials Calculator returns the quantity in the unit the supplier uses: cubic yards and bags for concrete, tons for gravel and asphalt, bags for mulch, and rolls or square feet for sod.
The site now has 21 calculators. The first eight (concrete, gravel, mulch, topsoil, sand, paver base, asphalt, sod) were joined by fill dirt, decomposed granite, river rock, riprap, road base, crushed concrete, pea gravel, lava rock, compost, stone dust, flagstone, mortar, and rebar. Each card on the homepage shows a worked example, such as a 10 by 10 ft slab at 4 in (1.36 cubic yards of concrete) or 500 standard bricks (17 bags of mortar).
Every result adds a waste allowance you control and prints the full calculation, so you can check it before you buy. The conversions use standard industry factors, written up on a methodology page. The site also carries material-type guides, for example concrete mix types, gravel types, and rebar sizes, so the number you get and the product you pick agree. The footer states the limit plainly: these are planning estimates, so confirm quantities with your supplier.