Mortar Calculator

Introduction

The Mortar Calculator helps you figure out how much mortar you need for your construction project. Mortar is the paste that holds bricks, blocks, and stones together. Getting the right amount is important — too little means extra trips to the store, and too much means wasted money. This tool lets you enter the size of your wall or project and quickly tells you how many bags of mortar mix you need to buy. Whether you are building a brick wall, laying blocks, or doing a small repair job, this calculator takes the guesswork out of planning your materials. Just plug in your numbers and get an accurate estimate in seconds.

How to Use Our Mortar Calculator

Enter your project details and wall dimensions below, and this calculator will tell you how much mortar you need — including total volume, weight, number of pre-mixed bags, and a breakdown of raw materials like cement, lime, and sand.

Unit System: Choose between Imperial (feet and inches) or Metric (meters and centimeters) to match how you measure your project.

Project Type: Select the tab that matches your job — Brick Wall, Block Wall, Stone Wall, Paving, Plastering, or Tiling. Each type has its own set of inputs.

Brick Size / Block Size: Pick a preset size like Standard or Modular, or choose Custom to type in your own width, height, and length. This helps the calculator figure out how much mortar fits between each unit.

Mortar Joint Thickness: Enter the thickness of the mortar joints between your bricks or blocks. A common value is ⅜ inch (about 1 cm).

Wall Length: Enter how long your wall is. You can add more wall sections if your project has multiple walls by clicking the "Add Another Wall Section" button.

Wall Height: Enter how tall your wall will be from bottom to top.

Wall Thickness: Choose Single Wythe (one layer of bricks or blocks), Double Wythe (two layers), or Custom to enter your own thickness value.

Stone Wall Thickness: For stone walls, type in the wall thickness directly since stone sizes vary.

Paving Inputs: Enter the area length, area width, joint width, joint depth, and the side length of your square pavers or flagstones. For more help sizing a paver project, try our Paver Calculator.

Plastering Inputs: Enter the wall length, wall height, and the thickness of the plaster coat you plan to apply.

Tiling Inputs: Enter the area length, area width, square tile side length, grout joint width, and bed thickness (the mortar layer under the tiles). You can also use our Tile Calculator to estimate tile quantities and our Grout Calculator to fine-tune grout needs.

Mortar Mix Type: Select the mix that fits your project. Type N is for general use, Type S is for structural work, Type M is for high-strength needs, and Type O is for interior jobs. Each type has a different ratio of cement, lime, and sand.

Waste Factor: Enter a percentage to account for spills, dropped mortar, and other waste. A value of 10% is a good starting point for most projects.

Calculate Mortar: Click this button to see your results, including mortar volume with and without waste, total weight, the number of pre-mixed bags needed in different sizes, and a full breakdown of raw cement, lime, and sand quantities.

What Is Mortar?

Mortar is the paste-like material that holds bricks, blocks, and stones together in construction. It is made by mixing cement, lime, sand, and water. When mortar dries, it creates a strong bond between masonry units and helps spread weight evenly across a wall. Without the right amount of mortar, a structure can crack, shift, or even collapse over time.

Common Mortar Mix Types

Not all mortar is the same. Different jobs call for different mix types, and each one has a specific ratio of cement, lime, and sand:

• Type N (1:1:6) – The most common general-purpose mortar. It works well for above-grade walls, chimneys, and outdoor projects. It offers a good balance of strength and flexibility.
• Type S (1:0.5:4.5) – A stronger mix used for structural walls, foundations, and retaining walls. It resists soil pressure and wind loads better than Type N.
• Type M (1:0.25:3.375) – The strongest standard mix. It is best for below-grade work like foundations and driveways where heavy loads press down on the masonry.
• Type O (1:2:9) – A softer, weaker mix used mainly for interior walls and non-load-bearing projects. It is easy to work with and good for repointing older brickwork.

Where Mortar Is Used

Mortar is needed in many types of construction projects beyond just brick walls. This calculator covers six common uses:

• Brick walls – Mortar fills the joints between bricks. A standard joint is about ⅜ inch thick. Single-wythe walls use one layer of brick, while double-wythe walls use two layers with mortar between them. Use the Brick Calculator to estimate how many bricks your wall requires.
• Block walls – Concrete blocks (commonly 8″ × 8″ × 16″) also require mortar in the joints. Because blocks are larger than bricks, fewer joints are needed per square foot, so less mortar is used.
• Stone walls – Natural stone shapes vary, so stone walls need more mortar to fill the gaps. Roughly 30% of a stone wall's volume can be mortar.
• Paving – Mortar fills the joints between pavers or flagstones. The amount depends on joint width, joint depth, and the size of the pavers.
• Plastering – A thin layer of mortar is spread over a wall surface to create a smooth finish. Plaster coats are usually ¼ to ½ inch thick.
• Tiling – Mortar serves as the bed that holds tiles in place, and grout (a form of mortar) fills the narrow gaps between tiles. Our Flooring Calculator can help you plan the full scope of a flooring project.

Why Accurate Mortar Estimates Matter

Ordering too little mortar means your project stops while you wait for more material. Ordering too much wastes money and creates cleanup problems, since mixed mortar begins to harden within 90 minutes. A good estimate saves time, reduces waste, and keeps your project on budget. Knowing the exact square footage of your walls or surfaces is the first step toward an accurate calculation.

Understanding the Waste Factor

In real-world construction, some mortar always gets wasted. It drops off the trowel, sticks to the mixing board, or dries out before it can be used. A waste factor of 10% is standard for most jobs. If you are working in hot or windy conditions where mortar dries faster, or if you are less experienced, increasing the waste factor to 15% or even 20% is a smart choice.

Pre-Mixed Bags vs. Raw Materials

You can buy mortar in two ways. Pre-mixed bags (such as 60 lb, 80 lb, or 94 lb bags) already contain cement, lime, and sand blended together—you just add water. They are convenient for small to medium jobs. For larger projects, buying raw materials separately (Portland cement, hydrated lime, and sand) is usually cheaper. This calculator shows both options so you can pick the best one for your project size and budget. If your project also involves pouring footings or foundations, our Concrete Calculator can help you estimate those material needs as well.

Frequently Asked Questions

What is the standard mortar joint thickness for bricks?

The standard mortar joint thickness for bricks is ⅜ inch (about 1 cm or 10 mm). This is the most common size used in residential and commercial brickwork. Some projects use ½ inch joints, but ⅜ inch gives a clean look and uses less mortar.

How many bags of mortar do I need per 100 square feet of brick wall?

For a single-wythe brick wall with standard bricks and ⅜ inch joints, you typically need about 6 to 8 bags of 80 lb pre-mixed mortar per 100 square feet. The exact number depends on your brick size, joint thickness, and waste factor. Use this calculator to get an accurate count for your specific project.

What is the difference between single wythe and double wythe?

A single wythe wall is one brick or block thick. A double wythe wall is two layers of bricks or blocks with mortar between them. Double wythe walls are stronger and provide better insulation, but they use roughly twice as much mortar and material.

How long does mixed mortar stay workable?

Mixed mortar stays workable for about 90 minutes to 2 hours. After that, it starts to harden and should not be used. In hot, dry, or windy weather, it can dry out even faster. Only mix as much as you can use within that time window.

Can I use the same mortar type for every project?

No. Different projects need different mortar types. Type N works for most general above-grade walls. Type S is better for structural and below-grade work. Type M handles heavy loads like foundations. Type O is only for interior, non-load-bearing walls. Using the wrong type can lead to cracking or failure.

How much water do I add to a bag of mortar mix?

Most mortar bags call for about 5 to 6 quarts of water per 80 lb bag. Always follow the directions on your specific bag. The mortar should be thick and hold its shape on a trowel without dripping. Add water slowly so you do not make the mix too thin.

What does the waste factor mean and what should I set it to?

The waste factor accounts for mortar that gets dropped, dries out, or sticks to tools during work. A 10% waste factor is a good default for experienced workers. If you are a beginner or working in hot or windy conditions, set it to 15% or 20% to be safe.

How do I calculate mortar for a wall with openings like doors and windows?

Measure the total wall area first, then subtract the area of each door and window opening. Enter the remaining wall dimensions into the calculator. You can also add multiple wall sections to account for the wall pieces around the openings separately.

Is mortar the same as concrete?

No. Mortar and concrete are different. Mortar is made from cement, lime, sand, and water. It is used to bond bricks, blocks, and stones. Concrete is made from cement, sand, gravel, and water. It is poured into forms for footings, slabs, and foundations. Mortar is not as strong as concrete but is more flexible.

Why does a stone wall need more mortar than a brick wall?

Natural stones have irregular shapes, so the gaps between them are bigger and uneven. About 30% of a stone wall's total volume can be mortar. Bricks are uniform in size, so the joints are thin and consistent, using much less mortar per square foot.

Can I switch between imperial and metric units?

Yes. Use the unit system toggle at the top of the calculator. Choose Imperial to enter measurements in feet and inches, or choose Metric to use meters and centimeters. The results will update to match your chosen unit system.

How do I know which bag size to buy?

The calculator shows how many bags you need in different sizes (60 lb, 80 lb, and 94 lb for imperial, or 25 kg and 50 kg for metric). Pick the size that is easiest for you to handle and that your store carries. Larger bags are usually cheaper per pound but heavier to lift.

What is the yield of an 80 lb bag of mortar?

An 80 lb bag of pre-mixed mortar yields about 0.56 cubic feet of mixed mortar. This is enough to lay roughly 25 to 30 standard bricks with ⅜ inch joints in a single-wythe wall.

Can I use this calculator for repointing old mortar joints?

Yes. Measure the wall area that needs repointing, then use the brick wall or block wall tab with your joint thickness. Since repointing only fills the outer portion of the joint (usually ¾ to 1 inch deep), you may want to reduce the wall thickness or use a custom setting to reflect the actual depth being filled.

What is the best mortar type for a garden wall?

Type N mortar is the best choice for most garden walls. It offers good strength and flexibility, handles weather well, and is easy to work with. If your garden wall also retains soil, use Type S for the extra structural strength.

How do I add more than one wall section?

Click the "Add Another Wall Section" button below your first wall section. You can add as many sections as you need. Each section has its own length, height, and thickness inputs. The calculator adds them all together for your total mortar estimate.