HowMuchIt / Concrete block
How many concrete blocks do I need?
1.125 standard blocks for every square foot of wall. Measure the wall, take off the openings, and the calculator gives the blocks and the mortar.
Work out your concrete blocks
Standard 8 x 8 x 16 in blocks (actual 7-5/8 x 7-5/8 x 15-5/8, with a 3/8 in joint): 1.125 per sq ft. Block makers' rule: about 3 bags of mortar per 100 blocks; your bag prints its own yield.
Why 1.125
A standard block is sold as 8 by 8 by 16 inches, but it really measures 7-5/8 by 7-5/8 by 15-5/8. The missing 3/8 inch is the mortar joint, so one block and its joints fill 8 by 16 inches of wall: 128 square inches, and 144 / 128 is 1.125 blocks per square foot.
Questions people ask
How many blocks for a 24 ft wall, 8 ft high?
192 sq ft x 1.125 = 216 blocks, plus a few extra.
How much mortar?
About 3 bags per 100 blocks by the block makers' rule; your bag prints its own yield.
Good to know
- A standard block is sold as 8 x 8 x 16 in (nominal) but actually measures 7-5/8 x 7-5/8 x 15-5/8 in.1,2
- The nominal size includes a 3/8 in mortar joint, the standard joint for block walls.1,2
- Plan on 1.125 standard 8 x 16 in blocks per square foot of wall face.3,4,5
- Wall area = length x height; subtract the area of doors and windows.5,6
- Block makers' rule of thumb: about 3 bags of mortar per 100 standard blocks.3,4
How we checked this page
Checked on October 27, 2026. We kept a fact only when two independent publishers agree, and each one is numbered to its sources below. Where sources give different numbers, we keep only what they share. We never write a price. This page was written with an AI assistant and checked against the sources below.
Sources
- Standard Cinder Block Dimensions, The Home Depot
- How to Build a Cinder Block Wall, Bob Vila
- Engineering Services Technical Bulletin: Rule of Thumb Conversion Factors, General Shale
- Titan America Block Estimating Guide, Titan America
- How To Calculate Concrete Blocks Needed For Your Next DIY Project, House Digest
- Brick Calculator, Glen-Gery