CMU Block Grout Calculator
Calculate cubic yards and bags of grout needed to fill concrete masonry block walls.
Cost Estimates
How It Works
This calculator estimates the volume of grout needed to fill concrete masonry unit (CMU) block wall cells based on wall dimensions, block width, and fill percentage.
How it works: Standard 8×16 CMU blocks have approximately 1.125 blocks per square foot of wall area. Each block's cell volume depends on the block width: 8" blocks have ~200 cu in per cell, 10" blocks have ~260 cu in, and 12" blocks have ~330 cu in.
Total grout volume = Wall Area × 1.125 blocks/sq ft × Cell Volume × Fill Percentage. The result is converted from cubic inches to cubic yards (divide by 46,656).
Pre-mixed 80 lb grout bags yield approximately 0.6 cubic feet each. For larger jobs, site-mixed grout is more economical.
Frequently Asked Questions
How much grout do I need to fill CMU block?
The amount depends on wall size, block width, and how many cells you fill. An 8" block has about 200 cubic inches of cell space per block. A standard 8x16 block wall has about 1.125 blocks per square foot of wall area. This calculator accounts for block width and fill percentage to give you cubic yards of grout needed.
Do I need to grout all the cells in a block wall?
Not always. Load-bearing walls and walls with rebar typically require 100% grout fill per building code. Non-structural walls may only need grouted cells at rebar locations (every 32" or 48" on center). Check your local building code and structural plans for specific requirements.
What is the difference between grout and concrete for filling block?
CMU grout is a fluid mix designed to flow into narrow block cells and around rebar. It has more water and smaller aggregate than standard concrete. Pre-mixed grout bags (80 lb) are convenient for small jobs. For large walls, site-mixed grout using sand, cement, and water is more economical.
How many 80 lb bags of grout fill a block wall?
An 80 lb bag of pre-mixed grout fills approximately 0.6 cubic feet. An 8" wide fully grouted wall needs roughly 1 bag per 3 blocks. A 10' x 8' wall (about 90 blocks) would need approximately 30 bags for 100% fill. Use this calculator for exact quantities based on your wall dimensions.