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Cinder Block Calculator

Estimate cinder blocks for walls and foundations.

Mason ReidFounder and Lead Estimator at MeasureThen

Last updated 2026-08-21

What Is a Cinder Block Calculator?

A cinder block calculator estimates how many cinder blocks you need to build a wall or foundation. It works the same way as a concrete block calculator because both share the same nominal 16 by 8 inch face size. Enter your wall dimensions and it gives you a count you can take straight to the supplier.

How It Works

Blocks = ceil(Wall area × 1.125) using the standard 16 × 8 in face.

Example

A 20 ft × 8 ft foundation wall needs 180 cinder blocks.

How to Calculate

  1. Measure the wall length and height in feet. A 20 ft long by 8 ft tall foundation wall covers 160 square feet.
  2. Choose the block size. The standard 8x8x16 cinder block covers 0.89 square feet per block.
  3. Multiply the wall area by 1.125 to get the block count.
  4. For 160 square feet, you need about 180 cinder blocks.
  5. Add 5% for cuts and chips, bringing the total to roughly 189 blocks.

Cinder Block Nominal Sizes

Nominal SizeActual Face (in)Blocks per Sq Ft
8x8x1615.625 x 7.6251.125
4x8x1615.625 x 7.6251.125
12x8x1615.625 x 7.6251.125
8x8x87.625 x 7.6252.25
8x4x16 (solid)15.625 x 3.6251.125

Sources

Frequently Asked Questions

Cinder or concrete block — what is the difference?

Cinder blocks are the lighter, older style; concrete blocks are denser and stronger. Both share the same nominal size.

How are blocks laid?

With mortar in a running bond, usually with cells aligned for optional reinforcing.

Do I need reinforcing?

Rebar and grout-filled cells are code-required for retaining and load-bearing walls in most areas.

Estimate the cost with the Masonry Cost Calculator or browse Masonry Calculators

More Masonry Calculators

Brick CalculatorCalculate how many bricks and bags of mortar you need for a wall. Enter wall dimensions and brick size to get your material quantity.Concrete Block CalculatorCalculate the number of concrete blocks needed.Mortar CalculatorEstimate the amount of mortar needed for a masonry wall.Masonry Cost CalculatorEstimate the cost of a masonry project.

Mason ReidFounder and Lead Estimator at MeasureThen

Mason Reid founded MeasureThen after two decades of hands-on work in construction and estimating. Across residential and light commercial projects, he sized concrete pours, framed walls, hung drywall, and priced out roofing, fencing, and deck work — learning the exact math that every job depends on. At MeasureThen he writes the formulas, checks every calculator against real-world assumptions, and makes sure each one is simple enough for a homeowner to trust and a contractor to use. When he is not measuring twice, he is helping projects stay on budget.

Every MeasureThen calculator uses simple, transparent formulas and standard industry assumptions drawn from common construction practice. We show the math behind each result and include worked examples so you can follow along and double-check the numbers. Results are estimates: materials, labor, and pricing vary by region and market, so always confirm important figures with a licensed professional and your local building codes.