Count standard 8×16 concrete masonry units for a wall from its length and height.
A standard 8×16 block with a 3/8" mortar joint covers 0.889 sq ft, so it takes 1.125 blocks per square foot of wall. Deduct openings and add waste for cuts and breakage.
1.125 blocks per square foot for standard 8x16 face blocks with 3/8" mortar joints.
800 sq ft × 1.125 = 900 blocks before waste; about 945 with 5% waste.
No. The count depends on the face size (8x16); width changes the weight, grout and cost per block, not how many you need.
Doing it from plans instead? Read How many CMU blocks do I need? Block count from plans, or see all free takeoff calculators.