Concrete Block Calculator - Calculate Concrete Blocks Needed

Concrete Block Calculator - Estimate Cinder Blocks & Mortar

Calculate the number of concrete blocks (cinder blocks) and mortar bags needed for your project. Get accurate estimates for walls, foundations, and retaining walls.

How to Use This Calculator

1. Measure Your Wall: Enter the length and height of your wall in feet
2. Account for Openings: Subtract the area of windows, doors, and other openings
3. Select Block Size: Choose standard 8x8x16 blocks or specify custom dimensions
4. Set Waste Factor: Add 5-10% for breakage and cuts
5. Get Results: See blocks needed and mortar requirements

Standard Concrete Block Sizes

Block Size	Dimensions	Common Use	Face Area
Standard	8" × 8" × 16"	General walls, foundations	0.89 sq ft
6" Block	6" × 8" × 16"	Non-load bearing walls	0.89 sq ft
10" Block	10" × 8" × 16"	Structural walls	0.89 sq ft
12" Block	12" × 8" × 16"	Foundation walls	0.89 sq ft

How Many Concrete Blocks Do I Need?

Formula:

Blocks = (Wall Area - Opening Area) ÷ Block Face Area × Waste Factor

Example Calculation:

• Wall: 20 ft × 8 ft = 160 sq ft
• Openings: 32 sq ft (1 door, 2 windows)
• Net Area: 160 - 32 = 128 sq ft
• Blocks (standard): 128 ÷ 0.89 = 144 blocks
• Add 10% waste: 144 × 1.10 = 158 blocks

Mortar Requirements

• Joint Size: Standard is 3/8" (0.375 inches)
• Coverage: ~30-35 sq ft per 80lb bag
• Per Block: ~40-50 standard blocks per 80lb bag
• For Example Above: ~3-4 bags of mortar

Types of Concrete Blocks

• Standard: Solid core, general construction
• Hollow: Two or three cores, lighter weight
• Partition: 4" wide, non-load bearing
• Lintel: U-shaped for door/window headers
• Corner: Square ends for corners
• Bullnose: Rounded corners for aesthetic

Installation Tips

• Always start corners with full blocks
• Stagger vertical joints (no aligned joints)
• Use string lines for straight, level courses
• Install horizontal reinforcement every 2-3 courses
• Fill cores with grout for reinforced walls
• Use control joints on long walls (every 20-25 ft)

Cost Considerations

• Block Price: $2-$5 per block (varies by size and type)
• Mortar: $5-$8 per 80lb bag
• Labor: $5-$10 per sq ft (installed)
• Additional: Rebar, grout, and supplies