8 Inch Cinder Block Calculator — Blocks & Mortar
Estimate 8-inch CMU blocks and mortar for screen, garden, and non-structural exterior walls under 6 ft tall. Includes waste factor and optional pallet count.
Enter Dimensions
Recommended: 10% for standard projects
Results
Blocks Needed
199blocks
Mortar Bags
7bags
60 lb bags · 1 bag per 30 blocks (NCMA)
Wall Area
160sq ft
Blocks per Sq Ft
1.125blocks/sq ft
BIA standard for 8×16 face
Editorial Standards
Each calculator is reviewed for formula accuracy, unit consistency, and alignment with current U.S. building practices before publication. We verify outputs against published engineering references and real-world project data. Learn more about our methodology.
8 inch CMU is the workhorse residential block — used for garden walls, garage walls, short basement walls, and screen walls under 6 ft tall. The 8-inch nominal depth provides good thermal mass and sound dampening at the lowest material cost per square foot of wall.
This calculator estimates 8 inch blocks using the standard BIA 1.125 blocks/sq ft factor. For load-bearing or retaining applications, switch to the 12 Inch Cinder Block Calculator.
How to Estimate 8 Inch Cinder Blocks
Block count = Wall Area × 1.125 × (1 + waste %). Mortar (60 lb bags) = ⌈Block count ÷ 30⌉.
8 Inch CMU Spec Quick Reference
- Nominal: 8 × 8 × 16 inches
- Actual: 7-5/8 × 7-5/8 × 15-5/8 inches
- Weight: ~30 lb hollow standard; ~25 lb lightweight; ~50 lb solid
- Coverage: 1.125 blocks per sq ft wall face
- Mortar: 1 × 60 lb Type S bag per 30 blocks
- Pallet: 90 or 108 blocks (supplier-dependent)
Frequently Asked Questions
What is the actual size of an 8 inch cinder block?
An 8 inch CMU has a nominal 8 × 8 × 16 inch dimension, but the actual size is 7-5/8 × 7-5/8 × 15-5/8 inches. The 3/8 inch difference is the mortar joint allowance — block + joint = nominal size.
Can I build a basement wall with 8 inch blocks?
8 inch CMU is permitted for short basement walls (under 5 ft of retained soil) in IRC R404.1 when properly reinforced. For taller walls or unbalanced fill depths above 5 ft, 12 inch CMU is typically required.
How much does an 8 inch cinder block weigh?
Standard 8-inch hollow-core CMU weighs ~30 lb. Lightweight blocks (made with shale or pumice aggregate) weigh ~25 lb. Solid 8-inch blocks weigh ~50 lb.
How many 8 inch blocks per pallet?
Most suppliers ship 8 inch CMU on pallets of 90 or 108 blocks. Confirm with your supplier when ordering — partial pallets often incur a surcharge.
How many blocks for a 20 ft × 8 ft wall?
20 × 8 = 160 sq ft × 1.125 = 180 blocks before waste. Add 10% waste for a straight wall = 198 blocks ordered.
Looking for the general calculator?
Estimate cinder blocks and mortar bags for any CMU wall. Supports 8-inch and 12-inch blocks with adjustable waste percentage and automatic pallet estimation.
Open the Cinder Block Calculator: Blocks & Mortar →