Concrete Block Calculator
Calculate the number of concrete blocks (CMU) needed for your wall project. Accurately estimate materials for retaining walls, foundations, and fences with waste allowances.
1. Wall Dimensions
2. Block Size
Note: These standard presets assume a default block width (thickness) of 8" (200mm) for mortar and fill estimation. To use a different width, switch to "Custom Size".
How to Use This Concrete Block Calculator
Planning a masonry project starts with accurate material estimation. Our concrete block calculator (often referred to as a cinder block calculator) helps you determine exactly how many concrete blocks do I need for your specific wall dimensions.
Unlike simple estimation methods, this concrete block wall calculator accounts for the mortar joints and allows you to include a waste percentage for cutting and breakage.
- Enter Wall Dimensions: Input the total length and height of the wall you are building.
- Select Block Size: Choose from standard concrete block sizes or enter custom dimensions.
- Review Results: Get the exact block count, mortar bags required, and core fill volume instantly.
Common Concrete Block Sizes
When purchasing materials, it is important to distinguish between "nominal" and "actual" sizes. Standard CMU (Concrete Masonry Unit) blocks are typically referred to by their nominal dimensions, which include the 3/8-inch mortar joint.
- 16" x 8" (Standard): The most common face size for structural walls.
- 8" x 8" (Half Block): Used for ends or staggering running bond patterns.
- 16" x 4" (Half Height): Often used for decorative courses or height adjustments.
Estimating Block Wall Cost
Calculating the material is the first step in budgeting. To find the total block wall cost, multiply your total block count by the local price per unit. Don't forget to factor in the cost of mortar and reinforcement bars (rebar).
If your wall requires a concrete footer (foundation), you can calculate the exact volume needed using our Concrete Calculator.
Example Calculation
Scenario: You are building a 50-foot long, 6-foot high privacy wall.
- Wall Area: 50' × 6' = 300 square feet.
- Block Face Area: A standard 16"x8" block covers approximately 0.89 sq ft.
- Result: You would need roughly 338 blocks. We recommend adding 5-10% for waste, bringing the total to ~355 blocks.
For projects involving poured concrete cores, you can verify your volume requirements with our Concrete Volume Calculator to ensure you order the right amount of ready-mix.
? Frequently Asked Questions
Divide your total wall area by the area of one block. For a standard 16x8 block, one block covers 0.89 square feet. For a 100 sq ft wall, you need roughly 113 blocks.
Yes. In 'Standard Mode', we use nominal dimensions (e.g., 16 inches long) which accounts for the standard mortar joint. We also calculate the total bags of mortar needed.
For simple straight walls, 5% is usually sufficient. If your wall has many corners, steps, or requires significant cutting, consider 10% or more.