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Concrete Block Calculator

Calculate concrete blocks and mortar bags for walls.

Last updated: June 13, 2026

Calculator

Wall Length

feet

Wall Height

feet

Block Size

Include Mortar?

Results

Blocks Needed180

Add 5-10% for waste: 199

Wall Area160 sq ft

Mortar Bags (80 lb)6 bags

~30 blocks per bag

Estimated Cost$360-$630

$2-$3.50 per block

How to Use This Calculator

1Enter the wall length in feet.
2Enter the wall height in feet.
3View the number of blocks, mortar bags, and cost estimate.

Formula Explanation

Standard CMU blocks are 8×8×16 inches (nominal), covering 1.125 sq ft each including mortar joints. Mortar is estimated at 3 bags per 100 blocks.

Blocks = (Wall Area sq ft) × 1.125 Mortar Bags = (Blocks ÷ 100) × 3

Variables:

Wall AreaLength × Height in square feet

Block Factor1.125 blocks per sq ft for standard 8×16 blocks

MortarApproximately 3 bags per 100 blocks

Worked Examples

30 ft long × 8 ft high wall

1. Area = 30 × 8 = 240 sq ft
2. Blocks = 240 × 1.125 = 270 blocks
3. Mortar = (270 ÷ 100) × 3 = 8.1 bags

Result: 270 blocks + 9 mortar bags (rounded up)

Why Use This Calculator

Accurate block count for ordering.
Includes mortar estimate.
Works for any wall dimensions.
Prevents costly over-ordering or project delays.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Tips & Best Practices

Order 5-10% extra blocks for breakage and cuts.
Use type S mortar for structural and below-grade walls.
Stack blocks in a running bond pattern for maximum strength.
Reinforce walls with rebar and grout in cells per local building codes.

Common Mistakes to Avoid

❌ Forgetting to subtract window and door openings.

✅ Calculate the area of each opening and subtract before computing block count.

❌ Ordering exactly the computed number of blocks.

✅ Add 5-10% for cuts at corners, ends, and breakage during transport.

Frequently Asked Questions

How many concrete blocks do I need per square foot?

Standard 8×8×16 blocks cover about 0.89 sq ft of wall face, so you need approximately 1.125 blocks per square foot of wall area.

How much mortar do I need?

Plan for approximately 3 bags (60-lb or 80-lb) of mortar mix per 100 standard blocks. This provides enough for 3/8-inch mortar joints.

Do I need to fill concrete blocks with grout?

Building codes typically require grouting and rebar in specific cells for structural walls, retaining walls, and in seismic zones. Check your local requirements.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

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Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

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