Enter the number of blocks to calculate how many bags of mortar mix you need.
How to Use the Block Mortar Calculator
Enter how many blocks you're laying, and the bag counts for all three standard mortar bag sizes appear together. The blocks-per-bag yield is editable if your mortar supplier publishes a different figure than the default.
Mortar coverage is quoted per block, not per square foot, because that's how mason's actually buy it — a bag lasts a certain number of blocks regardless of wall shape. 12.5 blocks per 80 lb bag is a widely used figure for standard 8x8x16 in. CMU laid with 3/8 in. joints and face-shell bedding, where mortar only sits under the block's outer face shells rather than filling the whole bed:
80 lb bags = ⌈(blocks × (1 + waste %)) ÷ blocks per bag⌉Full mortar bedding — filling the entire joint width instead of just the face shells — burns through mortar noticeably faster, and thicker-than-standard joints do too. If your project uses either, lower the blocks-per-bag figure rather than trust the default number here.