Build with confidence using the CalcGami Block Calculator. Estimate the exact number of concrete blocks (CMU) needed for walls or foundations, calculate mortar requirements, save your plans, and share material lists instantly via WhatsApp.
Calculation Result
Total Blocks Needed
0
BlocksIncludes wastage
Saved Calculations
| Date | Wall Size | Block Size | Result |
|---|
Related Calculators
Table of Contents
What is a Block Calculator?
A Block Calculator is a masonry estimation tool designed to determine the number of Concrete Masonry Units (CMUs) commonly known as cinder blocks or breeze blocks required to build a wall or foundation.
Unlike bricks, blocks are much larger and have standard dimensions (e.g., 8x8x16 inches). Calculating how many you need involves dividing the total wall area by the face area of a single block. However, accurate estimation must also account for mortar joints, wall openings (windows/doors), and wastage. This Block Calculator simplifies the math, providing a precise count of standard blocks and half-blocks. It includes History to track different wall sections, Save Calculation to organize your build, and WhatsApp Share to send the final order to your supplier.
Benefits of Using a Block Calculator
Whether building a retaining wall, a garage, or a garden bed, precision is key. Using this Block Calculator tool offers significant advantages:
- Cost Efficiency: Blocks are sold individually. Knowing you need exactly 450 blocks prevents you from buying 500 and wasting money on heavy leftovers.
- Mortar Estimation: It calculates the volume of mortar needed to bond the blocks, saving you a separate calculation for sand and cement.
- Opening Deductions: It subtracts the area of doors and windows, ensuring you don’t buy materials for empty space.
- Project Management: Use Save Calculation to store estimates for “North Wall” and “South Wall” separately.
- Fast Ordering: Use WhatsApp Share to send the material list directly to the lumberyard or masonry supply house to check stock availability.
Formula Used in Block Calculator
The Block Calculator uses the area method, adjusting for the standard 3/8-inch mortar joint included in nominal block sizing.
The Plain Text Formulas:
Step 1: Calculate Wall Area
Wall Area = Length x Height
Step 2: Calculate Block Area
Standard Block (Nominal) = 16 inches wide x 8 inches high = 128 sq inches = 0.889 sq ft.
(Nominal size includes the mortar gap).
Step 3: Calculate Net Blocks
Blocks Needed = Wall Area / 0.889
Step 4: Subtract Openings
Subtract (Window Area / 0.889) from the total.
Step 5: Add Wastage
Total Blocks = Net Blocks x 1.05 (5% for breakage/cuts).
How to Use the Block Calculator
Follow these steps to plan your masonry project:
- Enter Wall Dimensions: Input the Length and Height of the wall in feet.
- Select Block Size: Choose standard 8x8x16, or 4x8x16, etc.
- Add Openings: Enter the total square footage of any doors or windows to be subtracted.
- Calculate: Click the button to get the count.
- Review Results: View the total number of blocks and estimated mortar bags.
- Use Productivity Features:
- History: Review your last 5 calculations.
- Save Calculation: Name and save the project (e.g., “Retaining Wall”).
- Share on WhatsApp: Text the block count to your delivery driver.
Real-Life Example
Scenario:
“Frank” is building a garage wall. The wall is 20 feet long and 8 feet high. It has one door (3 ft x 7 ft). He is using standard 8x8x16 blocks.
The Calculation:
Step 1: Wall Area
20 ft x 8 ft = 160 sq ft.
Step 2: Door Area
3 ft x 7 ft = 21 sq ft.
Step 3: Net Area
160 – 21 = 139 sq ft.
Step 4: Blocks Needed
Standard block coverage is 0.889 sq ft per block.
Formula: 139 / 0.889
Calculation: 156.3 Blocks.
Step 5: Add Wastage (5%)
156.3 x 1.05 = 164 Blocks.
The Result:
Frank needs to order 164 Blocks.
- Action: Frank saves the calculation as “Garage Side Wall” and uses WhatsApp Share to send the order to the masonry supplier.
Frequently Asked Questions (FAQ)
What is a “Nominal” size?
A standard block is nominally 8x8x16 inches. However, the actual size is usually 7 5/8 x 7 5/8 x 15 5/8 inches. The missing 3/8 inch is to allow room for the mortar joint. The Block Calculator uses the nominal (larger) size because the block + mortar takes up 16 inches of space.
How many blocks are in a square foot?
For standard 8x8x16 blocks, you need 1.125 blocks per square foot of wall area.
Formula: 1 / 0.889 = 1.125.
Do I need concrete fill?
If the wall is structural or retaining soil, you often need to fill the hollow cores (“cells”) with concrete and rebar for strength. This Block Calculator estimates the blocks and joint mortar, not the core-fill concrete (grout).
Can I share the mortar estimate too?
Yes. When you use WhatsApp Share, the pre-filled message typically includes both the Block Count and the estimated Mortar Bags, so your supplier gets the full picture.
Does the history clear automatically?
History is usually stored in your browser’s temporary cache. It might clear if you restart your browser or clear cookies. Use the Save Calculation feature for permanent storage of important project data.
What about half-blocks?
Walls usually require half-blocks at the ends of alternating rows to keep the “running bond” pattern. You can estimate that roughly 10% of your order should be half-blocks or corner blocks, or simply cut standard blocks on-site.