Concrete Block Calculator

If you're planning a construction project and want to estimate how many concrete blocks you'll need, you're in the right place. Our Concrete Block Calculator is designed to make your job easier, faster, and 100% accurate. Whether you're a homeowner, contractor, or DIY builder, this tool saves time and eliminates guesswork.

Calculating the number of concrete blocks, cement, and sand for a project can be tricky, especially when you have to factor in wall dimensions, block size, mortar space, and waste. This is why we developed a free online concrete block calculator to help you plan with confidence and precision.

How to Calculate Concrete Blocks

To determine how many concrete blocks you need, you’ll first need to know the dimensions of your wall and the size of the blocks you're using. Here's the step-by-step concrete block calculation formula used in our calculator:

Wall Volume Formula:

Wall Volume = Length × Height × Thickness

Example:

A wall 20 feet long, 10 feet high, and 8 inches thick (0.666 ft):

Wall Volume = 20 × 10 × 0.666 = 133.2 cubic feet

Volume of One Block:

Standard 8x8x16 inch block:

Block Volume = 16 in × 8 in × 8 in = 1.33 ft × 0.666 ft × 0.666 ft ≈ 0.589 cubic feet

Number of Blocks:

Adjusted for mortar and waste (approx. 5%):

Number of Blocks = Wall Volume / Block Volume

= 133.2 / 0.589 ≈ 226 blocks

Adding 5% waste:

226 × 1.05 = ~237 blocks

How to Use the Concrete Block Calculator

Using our calculator is easy. Simply enter the wall’s dimensions and block size, and let the tool do the rest. Here's what it calculates:

• Total number of concrete blocks needed
• Estimated volume of mortar required
• Cement and sand quantities based on standard 1:4 mix
• Optional: price estimation if you input block or material costs

This calculator is ideal whether you're building a boundary wall, house wall, garden bed, or retaining wall.

Additional Construction Formulas

To help you even more, here’s how to estimate the mortar mix:

Mortar Volume:

Mortar Volume = Wall Volume - (Block Volume × Number of Blocks)

Example:

Mortar Volume = 133.2 - (237 × 0.589) = 133.2 - 139.5 = -6.3 cft (adjust wall or block size for accuracy)

If positive, convert it to dry volume using a factor of 1.33.

Then, using a cement:sand ratio of 1:4, divide accordingly.

Cement Volume = (Dry Volume / 5)

Sand Volume = (Dry Volume × 4 / 5)

To find the number of cement bags:

Cement Bags = Cement Volume / 1.226 (cft per 50kg bag)

Final Verdict

Concrete block construction is efficient, durable, and cost-effective but only when you plan it right. Our free Concrete Block Calculator ensures your calculations are precise, saving you money and materials. With easy-to-use inputs and accurate formulas, this tool is perfect for estimating blocks, mortar, and costs all in just seconds.

Don’t leave your construction estimates to chance. Use our calculator to plan better, build smarter, and finish faster.

FAQs

How do I calculate how many concrete blocks I need?

Use the formula:

Wall Volume ÷ Block Volume = Number of Blocks

Don’t forget to add 5–10% for breakage and waste.

How many blocks do I need for a 2000 sq ft house?

It depends on the height of the walls and number of rooms, but on average, you’ll need around 8,000–9,000 standard 8-inch blocks for a 2,000 sq ft house.

Is concrete block cheaper than poured concrete?

Yes, concrete blocks are generally more affordable and easier to handle than poured concrete walls, especially for smaller projects.

How many 8 inch blocks will a yard of concrete fill?

One cubic yard equals 27 cubic feet.

Divide this by the volume of one block (0.589 cft):

27 / 0.589 ≈ 45 blocks