Things to consider when laying asphalt:

• For every 1 inch of layer, add .25. Realistically, if you have 4 inches of loose asphalt, expect about a 2.75 to 3 inch final compaction. (results vary depending on asphalt type, weather, and geographic area.)
• These calculators factor in for relatively clean work areas. I.E., a square/rectangle/circular cut with an even depth all around.
• Always have the proper bonding agent applied to the surface before you apply the new asphalt.
• When using cold patch asphalt, heat with an external heat source and compact for best results.