Concrete Block Calculator

Created by Maria Kluziak
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Jan 04, 2023

If your plan is to build a concrete block wall, make sure to use this concrete block calculator before you lay the first stone! Is the question, "How many concrete blocks do I need for this project?" on your mind? If so, this tool will surely be of great help to you. You can use it to find out how many cinder blocks are needed for a wall of a particular size, estimate the required amount of mortar, and also get an idea of how much the materials needed for your project will cost based on the average concrete blocks cost.

🙋 Are you planning to use clay bricks instead? Then you can check our brick calculator for more brick-focused calculations.

How to use the concrete block calculator?

Our calculator is simple and intuitive to use. To estimate everything your project needs, just follow these instructions:

  1. Input the dimensions of the concrete block wall you're building, that is, its width and its height. They are needed for determining the wall's square footage.
  2. Decide whether you want to choose a preset block size, or input a custom one:
    • The preset block sizes are the six most common types you can find in the U.S.A. Feel free to use our length converter if you want to know what they are in metric. All you need to do here is pick the size you want.
    • If you pick custom size, you need to provide the calculator with the height and width of a single concrete block. An illustration of a wall segment will appear to show exactly which dimensions are needed, to avoid confusion.
    • In both cases, you will see the total number of concrete blocks needed for your project.
  3. Calculate the concrete blocks cost, which is done by inputting the price of a single block.
  4. Have a look at the mortar estimation field. On average, it takes three standard mortar bags to bond 100 concrete blocks together. Please note, that this is a rough estimation, and you might need to calculate it separately using factors such as mortar type.

🔎 For concrete blocks with void spaces in them, like in concrete hollow blocks (or CHBs), you can use our concrete block fill calculator to determine how much mortar you'll need to fill your blocks.

How many concrete blocks do I need?

If, after using our calculator, you're still thinking, "But how did they find out how many concrete blocks I need?", we are happy to walk you through the process!

When calculating the number of blocks needed, the first thing to do is to calculate the size of your concrete block wall. To do so, you need to multiply the wall's height and width:

wall size = wall height × wall width

To calculate the number of blocks, you need to divide the total area of the wall by the area of a single block:

number of blocks needed = wall area / block area

block area = block height × block width

Then you need to calculate your concrete block costs; just multiply the number of cinder blocks by the price per single block:

concrete block costs = price per block × number of blocks

When it comes to estimating the mortar needed, a good rule of thumb is that three standard bags will typically cover 100 blocks. To calculate the number of such bags, you need to divide the number of blocks by 33.3:

mortar bags estimation = number of blocks needed / 33.3

You can also use our cement calculator to find how much cement and sand you'll need if you decide to mix your own mortar for your concrete blocks.

Calculating concrete blocks - example

With the equations presented above, you can answer the question "How many concrete blocks do I need?" without too much trouble. Just in case, we will go through an example to clear up any doubts that may still remain.

Let's say your wall is to be 10 feet high and 50 feet wide. With these dimensions, it will cover 10 × 50 = 500 square feet. If you use a standard 16" x 8" block, the area of a single block is 128 square inches, and you will need 563 concrete blocks, as 500 ft² / 128 in² = 72,000 in² / 128 in² = 562.5 (rounding up to the nearest whole number).

If one cinder block costs $1.5, you will pay 563 × $1.5 = $844.5

As for the mortar bags estimation, dividing 563 by 33.3 results in 16.9. As you are limited to buying whole bags, you should get 17 standard bags of mortar for this particular wall.

A note on using the concrete block calculator

As with all construction projects, we advise that you buy at least 10% more material than you think needed in case of any unexpected mishaps. After all, it's better to be prepared beforehand rather than driving back and forth to the store and wasting time and gas.

If you need help calculating the right amount of additional materials, try using our percentage calculator.

FAQ

How many concrete blocks do I need to build a 10 square meter wall?

  1. Find how much area each block will cover. A 16 inch by 8 inch block covers 0.0826 square meters.
  2. Divide the desired wall area by the area per brick. In this case, we have 10 square meters divided by 0.0826 square meters, so we will need 121 concrete blocks.

How do I calculate the number of blocks that I need for my wall?

  1. Measure the size of the wall by finding its height and width. Use Omni's concrete block calculator multiply them together.
  2. Calculate the area of a block by multiplying its height and width.
  3. Divide your wall area by the block area. The result is the total amount of blocks you need.

How do I calculate the total cost of my wall?

  1. Determine how many blocks you will use by dividing the area of your wall by the area per block.
  2. Find out the price per block, then multiply the number of blocks by its unit price.
  3. The result represents the total block cost of your wall. This does not include other miscellaneous expenses like the mortar required.

How many bags of mortars do I need?

Usually, 100 blocks of 16 inches by 8 inches require three standard bags of mortar (40 kilograms). To be more precise, some mortar manufacturers recommend 26 bags per 1000 blocks, meaning 2.6 bags per 100 blocks.

Maria Kluziak
Wall calculations
Wall height
ft
Wall width
ft
Wall area
in²
Concrete block calculations
I want to
choose preset block size.
You can either choose from the common block sizes found in the U.S.A., or input a custom block size.
Block size
16" x 8"
Number of blocks needed
Costs calculations
Single block's price
$
Total cost
$
Mortar estimation
Standard bags of mortar
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