How much mortar do I need per cinder block?

Each standard 8x8x16 cinder block requires approximately 0.03 bags of 80-pound mortar (about 2.5 pounds of dry mortar mix), corresponding to 0.082 cubic feet of wet mixed mortar under standard 3/8-inch face-shell bedding.

How many bags of Quikrete do I need for 100 cinder blocks?

You need 3 bags of 80 lb Quikrete Mortar Mix (#1102 Type N) or Quikrete Mason Mix (#1122 Type S) per 100 standard 8x8x16 blocks. We recommend purchasing 4 bags of 80 lb to account for drop loss and joint striking waste.

How much sand and cement do I need for 100 cinder blocks?

For site-mixed scratch mortar conforming to ASTM C270 (1 part cement to 3 parts sand), 100 cinder blocks require approximately 1.3 bags (70 lb each) of Type S masonry cement and approximately 320 pounds (0.16 tons) of clean, damp masonry sand.

Should I use Type S or Type N mortar for cinder block walls?

Use Type S mortar (1,800 PSI compressive rating) for cinder block foundation walls, retaining walls, sub-grade basements, and structural walls. Use Type N mortar (750 PSI) for above-grade exterior walls, interior partition walls, and garden planters.

Cinder Block Mortar Focus

Mortar Calculator for Cinder Block

Q: How many blocks will an 80 lb bag of mortar lay?

One 80-pound bag of pre-mixed mortar yields approximately 0.67 cubic feet of wet mix and will lay 30 to 33 standard 8x8x16 concrete blocks with standard 3/8-inch face-shell bedding. If using full bedding on solid units, yield is approximately 22 to 25 blocks per bag.

Find exact bags of pre-mixed mortar (80 lb & 60 lb), Quikrete Mason Mix, scratch masonry cement, and sand tonnage for 4", 6", 8", and 12" cinder blocks.

Masonry Mortar Order Sheet

Generated by CinderCalc • cinderblockscalculator.com

Date: 10/22/2026

Standard: ASTM C270 Specification

Calculation Mode: Concrete Block (CMU)

Units to Lay: 150 units (150 units)

Joint Thickness: 0.375" Standard Bedding

Waste Factor: 10%

Total Mortar Volume: 3.69 cu ft

Total Wet Weight: 480 lbs (~0.2 Tons)

Material Item	Quantity Needed	Packaging	Specification
Option A: Pre-Mixed Mortar (80 lb)	6 bags	80 lb Pre-Blended Bags	Type S or Type N
Option B: Pre-Mixed Mortar (60 lb)	8 bags	60 lb Bags	Type S or Type N
Option C: Scratch Cement (70 lb)	2 bags	70 lb Masonry Cement	ASTM C91 Type S/N
Masonry Sand (For Scratch Mix)	0.24 tons (0.18 yd³)	Damp Loose Sand	ASTM C144 Sand
Mixing Water Required	~8 gallons potable water

Calculation Method

CMU Project Presets

Live Estimate

6Bags (80lb)(3.69 ft³)

Details

Total Cinder Blocks to Lay

Block Thickness

Joint Thickness

Cutting & Dropped Waste Factor (%)

Mortar Material Estimate

Pre-Mixed 80lb Bags (Type S / N)

Yielding 3.69 cu ft (covers ~150 units)

Pre-Mixed 60lb

8 bags

Mixing Water

~8 gal

Site Scratch Mix (1 Cement : 3 Sand)

Cement (70lb)

2 bags

Sand (Tons)

0.24 tons

Sand (Yd³)

0.18 yd³

Total Wet Weight

0.2 Tons (480 lbs)

Mortar Volume

3.69 cu ft

ASTM C270 Field Rule

One 80 lb bag lays ~30–33 standard 8" CMU blocks or 33–35 modular clay bricks with 3/8" joints.

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.

Quick Rule of Thumb: Mortar for 100 Standard 8x8x16 Cinder Blocks

80 lb Pre-Mix Bags

3 to 4 Bags

Order 4 bags for 10% waste

60 lb Pre-Mix Bags

4 to 5 Bags

Order 5 bags for 10% waste

Scratch Masonry Cement

1.3 Bags (70 lb)

Type S or Type N cement

Damp Masonry Sand

320 lbs

~0.16 tons of ASTM C144 sand

Type S vs. Type N Mortar for Cinder Blocks

Specification	Type S Mortar (Structural)	Type N Mortar (General)
28-Day Compressive Strength	1,800 PSI minimum	750 PSI minimum
Best Cinder Block Applications	Foundation walls, retaining walls, seismic zones, soil-contact walls	Above-grade partition walls, garden walls, decorative screen blocks
Bond & Lateral Strength	High flexural bond resistance to lateral soil & wind pressure	Moderate bond, high elastic workability and weather resistance
ASTM Standard	ASTM C270 Type S	ASTM C270 Type N

Laying Bricks or Calculating by Wall Square Footage?

If your project includes modular clay facing bricks, stone masonry, or direct square-footage wall estimation, use our Universal Masonry Mortar Calculator.

Universal Mortar Tool

Calculation Assumptions & References Planning Reference

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

Content date: March 2026

Related references: ASTM C270 (Mortar), ASTM C90 (CMU Units), Quikrete #1122 Specs, IRC Section R606. Confirm the applicable edition and local requirements.

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

Masonry Q&A

Frequently Asked Questions (Cinder Block Mortar)

Verified answers on bag yields per 100 blocks, Quikrete coverage, and sand-to-cement ratios.

For 100 standard 8x8x16 concrete blocks with standard 3/8-inch joints, you need exactly 3 bags of 80-pound pre-mixed mortar (or 4 bags of 60-pound mortar), plus a 10% waste buffer. In practice, contractors order 4 bags of 80 lb per 100 blocks to prevent running out during joint tooling.