🧱 Concrete Block Calculator
Calculate concrete blocks needed for your wall project
How to Use This Calculator
Enter Wall Dimensions
Input the length and height of your wall in feet. Measure the total wall area where you'll be installing concrete blocks. For multiple walls, calculate each wall separately.
Specify Block Size
Select your concrete block length and height in inches. Standard size is 16×8 inches, but blocks come in various sizes (8×4, 12×8, 16×8, etc.). Check your block specifications.
Calculate Blocks Needed
Click "Calculate Blocks" to see the total number of blocks needed. The calculator automatically accounts for 0.5-inch mortar joints between blocks.
Order Materials
Use the block count to order concrete blocks from suppliers. Add 10% extra for waste, cuts around openings (doors, windows), and mistakes. Also order mortar, rebar, and fill material if needed.
Formula
Effective Block Length = Block Length + Mortar Joint (0.5")
Effective Block Height = Block Height + Mortar Joint (0.5")
Blocks in Length = Wall Length (inches) ÷ Effective Block Length
Blocks in Height = Wall Height (inches) ÷ Effective Block Height
Total Blocks = Blocks in Length × Blocks in Height
Example 1: Standard Wall (20 ft × 8 ft, 16×8 inch blocks)
Step 1: Convert wall dimensions: 20 ft = 240 inches, 8 ft = 96 inches
Step 2: Effective block length: 16 + 0.5 = 16.5 inches
Step 3: Effective block height: 8 + 0.5 = 8.5 inches
Step 4: Blocks in length: 240 ÷ 16.5 = 14.5 → 15 blocks
Step 5: Blocks in height: 96 ÷ 8.5 = 11.3 → 12 blocks
Step 6: Total blocks: 15 × 12 = 180 blocks
Step 7: Add waste: 180 × 1.10 = 198 blocks (with 10% waste)
Example 2: Tall Wall (18 ft × 12 ft, 16×8 inch blocks)
Step 1: Convert wall dimensions: 18 ft = 216 inches, 12 ft = 144 inches
Step 2: Effective block dimensions: 16.5" × 8.5" (same as above)
Step 3: Blocks in length: 216 ÷ 16.5 = 13.1 → 14 blocks
Step 4: Blocks in height: 144 ÷ 8.5 = 16.9 → 17 blocks
Step 5: Total blocks: 14 × 17 = 238 blocks
Step 6: Add waste: 238 × 1.10 = 262 blocks (with 10% waste)
About Concrete Block Calculator
The Concrete Block Calculator is an essential tool for masons, contractors, builders, and DIY enthusiasts who need to accurately determine how many concrete blocks are required for their wall or structure projects. This calculator eliminates guesswork by providing precise block counts accounting for mortar joints, helping you order the right amount of materials without waste or shortages.
When to Use This Calculator
- Wall Construction: Calculate blocks needed for new walls, retaining walls, or foundation walls
- Structure Building: Determine materials needed for building block structures, sheds, or garages
- Garden Walls: Estimate block quantities for garden walls, privacy walls, or decorative features
- Foundation Work: Calculate blocks needed for foundation walls or basement walls
- Budget Planning: Calculate material costs by determining exact block quantities needed
Why Use Our Calculator?
- ✅ Accurate Block Count: Precise calculations prevent over-ordering or running short
- ✅ Mortar Joints: Automatically accounts for 0.5-inch mortar joints between blocks
- ✅ Multiple Block Sizes: Supports different block lengths and heights (8×4, 12×8, 16×8, etc.)
- ✅ Cost Planning: Helps budget accurately by determining exact material needs
- ✅ Time Savings: Instant calculations eliminate manual math and measurements
- ✅ Professional Results: Industry-standard formulas ensure contractor-quality estimates
Common Applications
Residential Walls: Homeowners and contractors planning new walls or replacing existing ones use this calculator to order the correct quantity of concrete blocks. Standard walls use 16×8 inch blocks, which this calculator helps determine accurately.
Retaining Walls: Contractors and homeowners planning retaining walls use this tool to estimate block quantities needed for larger structures. Retaining walls require proper foundation and may need rebar reinforcement.
Foundation Walls: Builders and contractors planning foundation walls or basement walls use this calculator to determine block quantities needed, ensuring sufficient materials are on-site before starting work.
Tips for Best Results
- Block Sizes: Standard is 16×8 inches, but blocks come in various sizes—verify your block specifications
- Add Waste: Always add 10% extra for waste, cuts around openings (doors, windows), and mistakes
- Account for Openings: Subtract door and window areas from total blocks for accuracy
- Mortar Needed: Calculate mortar separately—typically 1 cubic yard per 100 blocks
- Rebar & Fill: Plan for rebar reinforcement and block fill material if needed for structural walls
Frequently Asked Questions
How many concrete blocks do I need for a 20×8 foot wall?
A 20×8 foot wall using standard 16×8 inch blocks requires approximately 180 blocks (15 blocks in length × 12 blocks in height). Add 10% extra (18 blocks), so plan to order about 198 blocks total.
What size are standard concrete blocks?
Standard concrete blocks are 16 inches long × 8 inches high × 8 inches wide. They're called "standard" or "8×8×16" blocks. Half blocks (8×8×8) and other sizes are also available. Always verify your block specifications.
How do I account for doors and windows?
Calculate each wall section separately, or subtract door and window areas from total wall area. Standard doors are 32-36 inches wide (2-3 blocks), windows are 24-48 inches wide (1.5-3 blocks). Calculate openings separately for accuracy.
Do I need to add extra blocks for waste?
Yes! Always add 10% extra for waste, cuts around openings (doors, windows), and mistakes. If you need 180 blocks, order about 198 blocks (with 10% waste) to ensure you have enough material.
How much mortar do I need per block?
Approximately 0.01 cubic feet of mortar per block, or about 1 cubic yard of mortar per 100 blocks. Calculate mortar separately using a mortar calculator. Standard mortar mix is 1 part cement to 3 parts sand.
How much does a concrete block cost?
Concrete block prices vary by region and type: standard blocks $1-$3 each, decorative blocks $2-$5 each, colored blocks $3-$8 each. Prices depend on type, quality, and region. Get quotes from local suppliers.