How the calculation works
Tons of hot mix come from the volume of the mat and the weight of the mix:
Tons = square feet × (depth in inches ÷ 12) × density in lb/ft³ ÷ 2,000
Dividing the depth by 12 turns inches into feet, so square feet times depth gives cubic feet.
Cubic feet times density gives pounds, and 2,000 pounds is a ton.
Compacted hot mix is usually figured at 145 lb/ft³. Your plant can tell you the number for the
mix you're buying, and it's worth asking. At 140 instead of 145, the lot in the example below
comes to 175 tons instead of 181.
A worked example
A 10,000 sq ft parking lot at 3 inches compacted:
10,000 × (3 ÷ 12) × 145 ÷ 2,000 = 181.25 tons
Add 2 to 3 percent for waste and you're ordering 185 to 187 tons.
Depth moves the number most
Check the depth against the spec before you price anything. Typical compacted depths:
- 2 to 3 inches on a residential driveway
- 3 inches on a standard parking lot
- 4 inches or more where trucks, dumpsters or buses run
Each extra half inch on 10,000 sq ft is about 30 more tons. Price the lot at 3 inches, lay it at
3½, and that's 30 tons of mix nobody priced.
Before you call the plant
- Measure the gross area, then take out the islands, the building pads and anything else you
won't pave. - Figure each lift on its own if the spec calls for a binder course and a surface course. They're
often different mixes at different densities. - Add 2 to 3 percent for what stays in the truck bed, gets raked off the edges and ends up in
the low spots. - Ruts, potholes and a rough base take more mix than the flat math says. If the lot's in rough
shape, walk it before you trust the number.