# Mortar Calculator

Calculate mortar bags needed for brick and block walls. Get mortar volume, block/brick count, and cost estimate for standard brick, 8-inch, and 12-inch.

## What this calculates

Accurate mortar estimation prevents costly job-site delays. This calculator determines the number of 80-lb mortar bags needed for brick and concrete block (CMU) projects based on wall area, masonry unit type, and joint thickness, with an adjustable waste factor.

## Inputs

- **Wall Area** (sq ft) — min 0 — Total wall area to be laid with brick or block
- **Block Type** — options: Standard Brick (3.5" x 2.25" x 8"), 8" CMU Block (8" x 8" x 16"), 12" CMU Block (8" x 12" x 16") — Type of masonry unit
- **Joint Thickness** (in) — min 0.25, max 0.75 — Mortar joint width (standard is 3/8 inch / 10 mm)
- **Waste Factor** (%) — min 0, max 30 — Extra mortar for waste and tooling (10% typical)

## Outputs

- **Mortar Bags (80 lb)** — Number of 80-lb bags of pre-mixed mortar
- **Mortar Volume** (ft³) — Total mortar volume needed
- **Bricks / Blocks Needed** — Number of masonry units with waste factor
- **Estimated Mortar Cost** — formatted as currency — Approximate cost of mortar at $8 per 80-lb bag

## Details

Mortar requirements depend on the masonry unit size and joint thickness. Standard modular bricks (3.5" x 2.25" x 8") require about 3.5 cubic feet of mortar per 100 square feet of wall with 3/8-inch joints. Concrete masonry units (CMU blocks) use less mortar per square foot because fewer joints are needed for the same wall area.

Each 80-lb bag of pre-mixed mortar yields approximately 0.5 cubic feet when mixed. This calculator uses industry-standard coverage rates from the Brick Industry Association (BIA) and adjusts proportionally for non-standard joint thicknesses.

The waste factor (default 10%) accounts for mortar that falls during application, mortar left in the mixer, and mortar that sets before use. For experienced masons, 5-8% waste is typical. For DIY projects, consider 15% waste. In cold weather, mortar sets faster and waste increases. Plan for 12-15% in temperatures below 40°F.

## Frequently Asked Questions

**Q: How many bags of mortar do I need per 100 bricks?**

A: For standard modular bricks with 3/8-inch joints, you need approximately 7 bags (80 lb) of mortar per 100 square feet, which covers about 675 bricks. Per 100 bricks, that's roughly 1 bag (80 lb) of pre-mixed mortar, though this varies with joint width and waste.

**Q: What type of mortar should I use?**

A: Type N is the most common for general-purpose above-grade work (walls, chimneys). Type S is stronger and used for below-grade, structural, and high-wind areas. Type M is the strongest, used for foundations, retaining walls, and load-bearing applications. Type O is weakest, used for interior non-load-bearing walls.

**Q: How long does mixed mortar last?**

A: Pre-mixed mortar stays workable for about 1.5-2 hours in moderate weather (60-80°F). In hot weather or direct sun, it may set in 45-60 minutes. In cool weather, it lasts longer but sets slower. Never re-temper mortar that has begun to harden. Discard it and mix a fresh batch.

**Q: Can I use mortar instead of concrete?**

A: No. Mortar and concrete are different products. Mortar is designed to bond masonry units and is not suitable for structural applications like footings, slabs, or posts. Concrete contains gravel aggregate and achieves much higher compressive strength. Always use the product specified for your application.

**Q: How thick should mortar joints be?**

A: Standard mortar joints are 3/8 inch (10mm) for both bed (horizontal) and head (vertical) joints. Some applications use 1/2-inch joints. Thinner joints (1/4 inch) are used for thin-set brick veneer. Consistent joint thickness is important for structural integrity and appearance.

---

Source: https://vastcalc.com/calculators/construction/mortar
Category: Construction
Last updated: 2026-04-21