How much grout to fill one 8 inch block?
One standard 8 inch concrete block holds about 0.32 cu ft of grout when both cores are filled, by CMHA’s estimating table (3% waste included). That is about half an 80 lb bag of core-fill grout, so one bag fills roughly two blocks.
How to work it out
- 1 blocks ÷ 1.125 per sq ft × 36.1 cu ft per 100 sq ft (CMHA, 8 in, every core (solid grouted)) = 0.32 cu ft
- ÷ 0.68 cu ft per 80 lb bag = 1 bag
The per-block figure is handy for small jobs — a mailbox pillar, a gate post or a short run of reinforced cores — where you count blocks rather than square feet of wall.
Adjust for your project
- Grout volume (incl. 3% waste)
- 0.32 cu ft (0.0119 cu yd)
- Per block
- 0.32 cu ft
- Quikrete’s own estimate
- About 3 blocks per 80 lb bag of Core-Fill grout — 1 bags
Grout per block by width (solid)
| Block width | Per block | Grout volume (incl. 3% waste) |
|---|---|---|
| 6 in block | 0.23 cu ft | 0.23 cu ft |
| 8 in block | 0.32 cu ft | 0.32 cu ft |
| 10 in block | 0.42 cu ft | 0.42 cu ft |
| 12 in block | 0.52 cu ft | 0.52 cu ft |
Per block, by width
| Block | Grout per block (solid) | Blocks per 80 lb bag of grout |
|---|---|---|
| 6 in | 0.23 cu ft | 3.0 |
| 8 in | 0.32 cu ft | 2.1 |
| 10 in | 0.42 cu ft | 1.6 |
| 12 in | 0.52 cu ft | 1.3 |
Quikrete’s own estimate for its Core-Fill grout is about 3 standard blocks per bag, noticeably more than the CMHA arithmetic suggests. Real cores vary between block plants, and some of CMHA’s volume is the 3% waste. Use CMHA’s figure to be safe, or Quikrete’s and keep a spare bag.
Filling a single core
If only one core of the block is grouted — around a single bar, say — it takes roughly half the per-block figure. Rod the grout or tap the block so it fills the bottom corners. For whole walls, see how much concrete to fill 100 cinder blocks; for the blocks, how many blocks per square foot.
Different size? Use the full Block Fill (Grout) Calculator.
What you’ll need
- Drill mixing paddleBudget price
Mixes mortar, self-leveler, stucco and grout in a bucket. Use a low-speed, high-torque drill so the mix doesn’t fly.
See options on Amazon (opens in a new tab) - Mortar and concrete mixing tubBudget price
A wide, shallow tub for one or two bags at a time — easier to clean and to pull a hoe through than a wheelbarrow.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much grout to fill a 12 inch block?
About 0.52 cu ft per block, solid grouted.
How much grout to fill a 6 inch block?
About 0.23 cu ft per block, solid grouted.
How many bags of grout for 10 blocks?
5 bags of 80 lb core-fill grout (3.21 cubic feet).
Other common sizes
- How much concrete to fill 100 cinder blocks — About 32.1 cu ft: 54 bags of 80 lb concrete mix
Sources
- CMHA (formerly NCMA) TEK 04-02A — Estimating concrete masonry materials (opens in a new tab) — Each 8×16 unit covers 8/9 sq ft, so 112.5 units per 100 sq ft (119 with 5% waste); grout per 100 sq ft by unit width and core spacing (Table 3); cores filled per 80 lb grout bag (Table 4); one 80 lb bag of preblended mortar lays about 16 CMU with face-shell bedding (Table 2).
- Quikrete Core-Fill Grout (Fine, No. 1585-08) data sheet (opens in a new tab) — Each 80 lb bag yields about 0.68 cu ft and fills the cores of about 3 standard 8×8×16 blocks.
- Quikrete Concrete Mix (No. 1101) data sheet (opens in a new tab) — Yields: 40 lb ≈ 0.30, 50 lb ≈ 0.375, 60 lb ≈ 0.45, 80 lb ≈ 0.60, 90 lb ≈ 0.675 cu ft; unit weight ≈ 140 lb/cu ft; for pours 2 in thick or more; 6–9 pints of water per 80 lb bag; control joints every 6–8 ft; cure 5 days at 70 °F or above, 7 days at 50–70 °F; protect from freezing for 48 hours.