Concrete Block Calculator
How Many Concrete Blocks Do I Need?
Concrete blocks are an affordable building material that can be used for a number of construction projects, and are suited very well for construction walls for foundations or utility buildings. Concrete blocks typically have holes in the center to reduce the weight, material needed, and cost. The average concrete block is composed of cement and coal ash, which is why they are often called cinder blocks. Concrete blocks are actually concrete masonry units, or CMUs, but we often refer to them concrete blocks or cinder blocks Learn more about concrete masonry units
Finding how many concrete blocks you need for your project can seem like a confusing and challenging task, but it can be simplified using the calculator above. Simply enter the dimensions for your wall project and the concrete block calculator will figure out how many blocks are needed. For example, a 10′ x 10′ wall using a 16″ x 8″ x 8″ block will require an estimated 120 blocks and cost about $120 for material. If you’re building a retaining wall then check out our retaining wall calculator. Consider getting several professional estimates to get the best labor cost and find the right company for your project. A wall typically costs $10 – $15 to install, learn more about the cost factors of a wall project.
Figuring Out How Many Concrete Blocks You Need
There are several formulas to figure out how many blocks are needed for a wall project, but the first step is to determine the width and height of the wall, in inches.
Once you know the size of your wall, calculate the square footage by multiplying the width(in feet) times the height(in feet).
Now you need to figure out the square footage of block you are using. The standard block size is 16″ wide x 8″ high. Multiply 16×8 and then divide by 144 to get the answer, ie. (16*8)/144 = .89. Different size blocks will have different square footages, apply the formula above to find the answer. Check out our square footage calculator to find the square footage of your block.
After you have found the square footage of both your wall and your block, determining the number of blocks you need is as simple as dividing the wall square footage by the block square footage, ie. (wall ft^{2}) / (block ft^{2}). It is recommended to add 5%-10% additional blocks to account for broken blocks or blocks that need to be cut for the edges.
Our calculator above may indicate a different quantity of blocks needed since it uses a more precise formula, accounting for partial blocks and cutoffs automatically.
Installation Tools Needed to Install Concrete Block Wall
If you’re installing a concrete block wall you will need several tools to do the job correctly. Here is a small list of tools that are necessary to build a wall.
- Brick Trowel: This is used to lay an even bed of mortar when setting block.
- Mason Line: Use mason line to make sure the wall is straight and level and to ensure the block is set at an even height.
- Level: Make sure you have a level on hand to verify that each block is straight and level with adjacent blocks.
- Jointer: A jointer will help get smooth, clean joints for a nice look.
- Tape Measure: You’re definitely going to need a tape measure for this one.
- Mixing Tub: Mix mortar in a mixing tub to keep your wheelbarrow clean.
Common Concrete Block Sizes
You’ll need to know the size of the concrete block you’ll be using in order to determine how many blocks you need for your project. The most common sizes are 8″ high by 8″ wide and 8″ high by 16″ wide in varying thicknesses. The thickness of the block is not critical to finding how many blocks you need but it is important when estimating how much mortar and other masonry material you need. The common thicknesses are 4″, 6″, 8″, 10″, 12″, and 14″. Refer to the table below for standard block sizes including the nominal sizes. The nominal size is the actual size of the block, while the size includes a 3/8″ mortar joint and is the size that should be used when estimating material. The standard mortar joint should be 3/8″ thick for your wall.
2″ and 3″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
2″ x 8″ x 16″ | 1 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
3″ x 8″ x 16″ | 2 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
4″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
4″ x 8″ x 8″ | 3 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” | 226 |
4″ x 8″ x 16″ | 3 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
6″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
6″ x 8″ x 8″ | 5 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” | 226 |
6″ x 8″ x 16″ | 5 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
8″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
8″ x 8″ x 8″ | 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” | 226 |
8″ x 8″ x 16″ | 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
10″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
10″ x 8″ x 8″ | 9 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” | 226 |
10″ x 8″ x 16″ | 9 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
12″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
12″ x 8″ x 8″ | 11 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” | 226 |
12″ x 8″ x 16″ | 11 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
14″ CMU | ||
---|---|---|
Size D x H x W | Nominal D x H x W | Blocks per 100 ft^{2} |
14″ x 8″ x 8″ | 13 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” | 226 |
14″ x 8″ x 16″ | 13 ^{5}⁄_{8}” x 7 ^{5}⁄_{8}” x 15 ^{5}⁄_{8}” | 113 |
Estimating Block Mortar Needed
Estimating the amount of mortar needed for the joints in a concrete block wall will vary depending on the mortar mix you use. A general rule of thumb is to divide the number of blocks by 10 to get the number of 60 pound bags of mortar you’ll need, assuming you’re using an 8″ x 8″ x 16″ block. This calculation will vary so be prepared to calculate this based on the mix and size of block. You may need other masonry material, such as sand or portland cement as well depending on your mortar mix.
Check out our concrete calculator to help with your other concrete projects.
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