What Is the Mortar Calculator?
The Mortar Calculator is a free online tool designed for contractors and DIY builders who need quick, accurate calculations in the construction and building space. By entering your wall area, brick / block size, mortar joint thickness, you get instant results including mortar bags, sand needed, water. No formulas to memorize, no spreadsheets to build — just enter your numbers and get the answer in seconds. Whether you're a beginner or experienced professional, this calculator saves you time and eliminates guesswork.
Why This Calculation Matters
Getting mortar bags right can make the difference between success and costly mistakes. In construction and building, small errors compound quickly. Manual calculations are error-prone and time-consuming, especially under pressure. This calculator applies proven formulas used by contractors and DIY builders worldwide, giving you confidence that your numbers are correct. Use it to plan your projects with precision and avoid common pitfalls that trip up beginners.
When Should You Use This Calculator?
This tool is most useful when you know your wall area and need to find the right mortar bags. It's also great for quick estimates before committing to a decision, and to double-check manual calculations or professional quotes, and when comparing different scenarios side by side. Bookmark this page and come back whenever you need a fast, reliable answer — the calculator is always free and requires no signup.
Mortar Calculator
How to Use This Calculator
- Enter Your Wall Area (sq ft): Start by entering your wall area — this is the primary input for the calculation.
- Fill In Additional Details: Complete the remaining fields: brick / block size, mortar joint thickness, price per bag. Each value refines the calculation for greater accuracy.
- Click Calculate: Hit the Calculate button to run the numbers. Results appear instantly below.
- Review Your Results: Check your mortar bags, sand needed, water. Use these figures to inform your next decision or compare against alternative scenarios.
How to Calculate Mortar
Mortar calculations are based on wall area divided by the coverage per bag for your unit type and joint thickness.
- Standard brick, 3/8" joint: ~35 sq ft per 80 lb bag
- Standard brick, 1/2" joint: ~25 sq ft per bag
- CMU block, 3/8" joint: ~12 sq ft per bag
- Sand: ~0.5 cu ft per bag (for site-mixed mortar)
- Water: ~1.25 gallons per 80 lb bag
- Add 10% for waste, drops, and repointing
Tips & Considerations
- Double-check your wall area before calculating — even small input errors can significantly change your results.
- Run the calculator with different values to compare scenarios and find the optimal approach for your situation.
- Pay attention to both mortar bags and sand needed — they work together to give you the full picture.
- Bookmark this page for quick access next time you need to plan your projects.
- If you're unsure about your price per bag, start with a conservative estimate and adjust from there.
Frequently Asked Questions
How much mortar per square foot of brick?
About 1 bag per 35 sq ft with standard bricks and 3/8" joints. With 1/2" joints, plan 1 bag per 25 sq ft. Coverage varies with brick size and mortar consistency.
How much sand for mortar?
Premixed bags need no extra sand. For site-mixed mortar, use 3 parts sand to 1 part cement. Plan about 0.5 cu ft of sand per 80 lb bag equivalent.
How much water per bag?
About 1.25-1.5 gallons per 80 lb bag. Add gradually until you reach a butter-like consistency. Too much water weakens the mortar.
What mortar type should I use?
Type S for structural and below-grade walls (2,300 psi). Type N for non-load-bearing above-grade walls (750 psi). Type M for heavy loads and foundations.
How long is mortar workable?
About 1.5-2 hours in normal conditions. Under 1 hour in hot weather above 90°F. Mix only what you can use in 90 minutes.
How much mortar for CMU blocks?
One 80 lb bag covers 12-14 standard 8×8×16 blocks (about 12 sq ft of wall). Blocks require less mortar per sq ft than bricks due to fewer joints.