How block counts are calculated
Wall area divided by the area one block covers. A standard 8 x 8 x 16 inch block plus its 3/8 inch mortar joint covers about 0.95 sq ft, so a 10 ft x 4 ft wall needs about 42 blocks before waste. The calculator adds your waste allowance (5% is typical) for cuts and breakages.
Mortar is estimated at one 80 lb bag per 32 blocks. For a structural wall, check local code for reinforcement, footing depth and grout fill — block walls that hold back soil or support a load are not a DIY guess.
Pouring concrete instead? Try the concrete calculator.