How many blocks can you fill with one cubic yard of concrete grout?

One cubic yard of concrete contains 27 cubic feet. Since a standard 8-inch block holds 0.22 cubic feet of grout, one cubic yard will fill approximately 122 blocks completely, assuming zero waste.

What is the difference between grout and standard concrete?

Masonry core-fill grout (ASTM C476) is highly fluid with a high slump of 8 to 11 inches and contains small pea gravel aggregate (≤ 3/8-inch). This fluidity allows it to flow freely around vertical rebar and tie wires without creating honeycomb voids.

What is the compressive strength requirement for ASTM C476 grout?

Specify grout to the applicable ASTM C476 and TMS 402/602 edition and the project documents. The designer establishes required grout strength for the assembly; f'm denotes specified masonry assembly strength, not unit strength.

How do you calculate grout for partially grouted walls?

For walls with vertical rebar spaced every 32 inches on-center, only 1 out of every 4 cores is grouted (since each 16" block contains 2 cores). Divide the total wall core volume by 4, and add the volume of any continuous horizontal bond beams.

Structural Grouting Tool

Cinder Block Grout Calculator

Calculate the volume of concrete grout required to solidify your masonry wall cores under ASTM C476 standards. Supports fully or partially grouted designs across all block sizes.

Concrete presets

Live Estimate

0.9yd³ Grout(41 bags)

Details

Total Cinder Blocks in Structure

Block Thickness

Grouting Density

Waste Buffer (%)

Grout Estimate

Total Volume (Cubic Yards)

0.9 yd³

yielding 24.2 cubic feet

Pre-mixed 80lb

41 bags

Pre-mixed 60lb

54 bags

Raw Scratch Mix (1:2:3 Concrete)

Cement (94lb)

7 bags

Sand (tons)

0.67 tons

Gravel (tons)

0.98 tons

Total Wet Weight

1.8 tons

Pallet Count

1 pallets

Concrete Density Note

Calculations assume standard masonry core volumes. Wet concrete weighs roughly $145$ lbs per cubic foot.

CMU estimates use nominal face dimensions and illustrative mortar yields (30 standard 8-inch units per 80-lb premix bag before waste; thickness adjustments apply). Confirm product yields, unit core volumes, supplier pack sizes and local prices before ordering. Reinforcement quantities are material allowances; laps, hooks, embedment and engineered design are excluded.

Core Fill Volume by Block Thickness

CMU Block Size	Volume per Block	Blocks Filled per Cu Yd	Grout per 100 Blocks	80lb Bags per 100 Blocks
6" × 8" × 16"	0.15 cu ft	~180 blocks	0.56 cu yds	~25 bags
8" × 8" × 16"	0.22 cu ft	~122 blocks	0.81 cu yds	~37 bags
10" × 8" × 16"	0.28 cu ft	~96 blocks	1.04 cu yds	~47 bags
12" × 8" × 16"	0.35 cu ft	~77 blocks	1.30 cu yds	~59 bags

How to Calculate Core Fill Grout Volume

Concrete core grouting reinforces hollow masonry walls against extreme shear forces, wind uplift, and hydrostatic earth retention. Follow this professional workflow:

Determine Gross Block Quantity

Count all hollow blocks in the wall envelope. Note block thickness (6", 8", 10", or 12").

Identify Reinforcement Spacing

Determine whether engineering specifies solid grouting (100% cores) or reinforced spacing (every 32" or 48" OC).

Calculate Net Core Volume

Multiply core count by unit core volume (0.22 cu ft for 8" CMU) to determine cubic footage.

Convert to Cubic Yards

Divide cubic feet by 27 to obtain ready-mix delivery yards. Add 10% for jobsite spills and pump priming.

Verify ASTM C476 Slump

Ensure grout slump measures 8 to 11 inches so it consolidates smoothly around rebar without voids.

Mechanical Consolidation

Consolidate each grout lift with a 3/4-inch pencil vibrator to eliminate hidden air pockets.

ASTM C476 Grouting Field Standards

High Slump Requirement: Masonry grout requires an 8-inch to 11-inch slump because dry porous concrete blocks rapidly absorb water from the wet mix upon contact.
Clean-Out Openings: When pouring grout in high-lift pours exceeding 5 feet, building codes require clean-out holes at the base of every reinforced cell to remove mortar droppings before grouting.
Fine vs Coarse Grout: Use fine grout (pea gravel ≤ 3/8") for grout spaces under 2 inches wide, and coarse grout for larger voids in 10-inch or 12-inch CMU cores.
Never Use Standard 4" Slump Concrete: Standard slab concrete is too stiff to fill narrow hollow cells and will bridge over rebar, leaving dangerous structural voids.

2026 Concrete Grout Pricing

In 2026, ready-mix pea gravel grout delivered by transit mixer averages $140 to $175 per cubic yard. For small projects mixing 80 lb pre-blended core-fill bags on site, bags retail for $5.50 to $7.00 each.

Calculation Assumptions & References Planning Reference

Material estimates depend on the selected dimensions, product yields, and waste allowance.

Content date: March 2026

Related references: ASTM C476 (Grout for Masonry), ASTM C90 (CMU Units), TMS 402/602, IRC Section R606. Confirm the applicable edition and local requirements.

A material estimate is not a structural design or code approval.

Masonry Q&A

Cinder Block Core Fill FAQ

Verified answers on core volumes, slump criteria, and cubic yard calculations.

For a standard 8x8x16 concrete masonry unit (CMU), the internal volume of the two hollow cells combined is approximately 0.22 cubic feet. Therefore, filling 100 blocks completely requires 22 cubic feet, or about 0.81 cubic yards of concrete grout.