How to Calculate Mortar for Cinder Blocks
Estimating mortar accurately is just as important as counting your blocks. Ordering too little can halt your project, while ordering too much leads to waste and extra disposal costs. The amount of mortar you need depends primarily on the number of blocks and the thickness of your mortar joints (standard is 3/8").
The Standard Mortar Rule
For standard 8x8x16 cinder blocks, the rule of thumb is that one bag of pre-mixed mortar (80lb) covers approximately 12 to 15 blocks. This varies slightly based on how thick you apply the mortar and how much waste occurs during the spreading process.
Mortar Types
Type N: Best for general masonry and above-grade walls.
Type S: Higher strength, ideal for below-grade foundations or retaining walls.
Yield Estimates
100 Blocks = ~8.5 Cubic Feet of Mortar.
500 Blocks = ~42 Cubic Feet (Approx. 1.5 Cubic Yards).
Step-by-Step Mortar Estimation
- Count your blocks: Use our Cinder Block Calculator first to get your total block count.
- Factor in Waste: Always add 10-15% for mortar waste, as it often falls inside the block cores or is scraped off.
- Choose your mix: Decide if you are using pre-mixed bags or mixing cement and sand yourself.