ICF Calculator

1. Enter the wall length and height in feet, and the total openings area to subtract.
2. Check the block height, block length and core width against your manufacturer’s data.
3. Set a block waste and a concrete waste allowance.
4. Read the blocks to order, the courses, and the core concrete in cubic yards.

Here is what each result line means:

An ICF calculator estimates the materials for an insulated concrete form wall. ICF blocks are hollow forms made of two foam panels held apart by ties; they are stacked like large building blocks, reinforced, and filled with concrete. The foam stays in place as insulation.

Two quantities matter: how many blocks cover the wall, and how much concrete fills the core. Both follow from the wall area and the block dimensions. To order the concrete, the concrete truck calculator turns yards into truck loads, and the concrete pump cost calculator budgets the pump that ICF walls usually need.

Blocks tile the wall, so the count is the net wall area divided by the face area of one block. A 16 by 48 inch block has a face of 768 square inches, or 5.33 square feet.

1. Subtract openings from the wall area for the net area.
2. Divide by the block face area, add the block waste and round up.
3. Multiply the net area by the core width in feet for the core volume, divide by 27 and add the concrete waste.
4. Divide the wall height by the block height for courses, and the length by the block length for blocks per course.

For the weight of the finished wall, the concrete weight calculator gives the tonnage.

Suppose you are building a wall 40 feet long and 9 feet high with 30 square feet of openings, using 16 by 48 inch blocks with a 6 inch core and 5 percent waste on each.

Calculation: the net area is 40 x 9 – 30 = 330 sq ft. Each block covers 5.333 sq ft, so the raw count is 61.9 and, with 5 percent waste, 65 blocks. The core is 330 x 0.5 = 165 cubic feet, or 6.11 cubic yards, about 6.42 cu yd with waste. The wall is 7 courses high, the top one cut down, and 10 blocks per course.

The lesson: a 6 inch core uses half a cubic foot of concrete per square foot of wall, so one cubic yard fills about 54 square feet.

Core Width

Concrete scales directly with the core. An 8 inch core uses a third more concrete than a 6 inch core for the same wall area, while the block count stays the same.

Block Size

Block face sizes vary between manufacturers. Enter your block’s height and length, since a slightly different face changes the count.

Corners and Specialty Blocks

Corners, tee walls and brick-ledge blocks are separate items. Count them from your plans and reduce the straight blocks to match.

Openings and Bucks

Doors and windows need bucks framed into the wall. Subtracting their area keeps the block and concrete counts honest.

An ICF wall sits between a poured wall and a block wall: it is stacked like block but filled solid like a poured wall.

For the other two, use the concrete wall and concrete block calculators in the related tools.

Ordering Blocks

Turn the wall into a block count before you order, then add corners and specialty blocks from your plans.

Ordering Concrete

The core volume sizes the ready-mix order and tells you whether a pump and more than one truck are needed.

Comparing Core Widths

See how much more concrete a wider core needs before you settle the design with your engineer.

1. Using the Overall Block Width

Concrete depends on the core width between the foam, not the overall block thickness. Use the core figure.

2. Forgetting Corner Blocks

Corners are separate blocks. Count them from the plans so the total matches what gets stacked.

3. Not Subtracting Openings

Large windows and doors remove both blocks and concrete. Leaving them in over-orders both.

4. Short-ordering Concrete

Running out partway up an ICF pour leaves a cold joint. Keep a waste allowance and confirm the order before the trucks arrive.

5. Treating the Estimate as a Design

Reinforcement, bracing and pour lifts come from the manufacturer and the engineer, not from this tool.

The geometry is exact for straight blocks; the counts depend on the block data you enter.

Divide the net wall area by the face area of one block and add about 5 percent waste. A 16 by 48 inch block covers 5.33 square feet, so a 330 square foot wall needs about 62 blocks, or 65 with waste, plus any corner blocks.

Multiply the net wall area by the core width in feet and divide by 27 for cubic yards. A 6 inch core takes half a cubic foot per square foot of wall, so one cubic yard fills about 54 square feet.

A 16 by 48 inch block with a 6 inch core holds about 5.33 x 0.5 = 2.67 cubic feet, or roughly 0.099 cubic yards. Check your block’s data sheet for its stated figure.

Many standard ICF blocks have a face of 16 by 48 inches, but sizes vary between manufacturers. Enter your block’s height, length and core width for an accurate count.

No. It counts straight blocks by area. Corners, tee walls and specialty blocks are counted separately from your plans; reduce the straight blocks accordingly.

Divide the wall height in inches by the block height. A 9 foot wall with 16 inch blocks is 6.75 courses, so 7 courses with the top one cut down.

About 5 percent for blocks and 5 percent for concrete is a reasonable starting point for a simple wall. Walls with many openings and corners need more.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Insulating Concrete Form Manufacturers Association (ICFMA; industry information on ICF construction).
• American Concrete Institute (ACI; concrete walls and reinforced concrete practice).
• American Cement Association (American Cement Association; concrete construction basics).