Masonry & concrete · free tool
Mortar Calculator
How much mortar do you need? Enter your blocks, bricks or wall size, pick your bag and mortar type, and get bags — or the exact cement, lime and sand to mix on site.
Mortar Calculator
How many bags of mortar you need — or the mix.
1 Your project
2 Mortar
3 Your estimate
80-lb Type N — about 1 bag per 12 blocks.
An 80-lb bag lays about 12 blocks at a 3/8 in joint; a 60-lb bag about 8. Add 10-15% for drops and tooling — already included.
Approx. 1 bag of cement, 40 lb lime and 0.22 yd³ of sand — ratios and yields vary, so mix to a workable, fatty consistency.
Estimates only — bag yields, joint size and waste vary; confirm the bag's stated coverage before ordering. See how we calculate · Updated monthly
Method · how it works
How to calculate how much mortar you need
Count the units, divide by what a bag lays, add for waste. Here is exactly what the calculator does.
Count the units
Enter blocks or bricks — or a wall size. We auto-count at 1.125 block or 6.55 brick per sq ft.
Divide by bag yield
An 80-lb bag lays about 12 blocks or 36 bricks at a 3/8 in joint; a 60-lb bag less.
Add for waste
Add 10-15% for drops, premature set and joint tooling — you can't mix a half bag mid-course.
Or mix your own
Prefer site-mix? We split the volume into cement : lime : sand by your mortar type.
A 100-block wall, 80-lb bags
× 1.10 waste = 9.2
round up = 10 bags
80-lb pre-mixed, 3/8 in joint
Sources: Inch & Omni masonry tables · ASTM C270 mortar types · supply-house estimating guides
Reproduces published 80-lb bag tables · Updated monthly
Estimates only. Bag yields vary by brand, joint size and unit dimensions — always check the yield printed on the bag, and buy the waste shown so you don't run short mid-wall. For odd sizes the tool also supports a volume method.
Reference · 3/8 in joint
Bags of mortar by the job
Pre-mixed bags for a standard 8×8×16 block and modular brick wall. The tool adjusts for your bag size, mortar type and waste.
Concrete block
100 block
200 block
300 block
Modular brick
500 brick
1,000 brick
1,500 brick
Rule of thumb: ~12 blocks or ~36 bricks per 80-lb bag. Figures are before waste — add 10-15% on top (the tool does). A 1/2 in joint uses about 1.33× the mortar of a 3/8 in joint.
Pick the right mix
Mortar types: O, N, S and M
The letters come from the word MASONWORK. Each is a cement-lime-sand ratio with a different strength — match it to the job, not just the highest number.
1 : 2 : 9
cement : lime : sand
Interior, non load-bearing. Repointing soft or historic brick where a hard mortar would crack the units.
1 : 1 : 6
cement : lime : sand
General above-grade. Brick, block, chimneys and exterior walls — the safe all-rounder when in doubt.
2 : 1 : 9
cement : lime : sand
Below-grade, load-bearing. Foundations, retaining walls, patios and anything taking soil or structural load.
3 : 1 : 12
cement : lime : sand
Heavy load / below-grade. Foundations, driveways and hardscape carrying serious weight.
Higher strength isn't always better. The mortar should be a touch weaker than the masonry so the joint — not the brick or block — is what moves and can be repaired. When you're unsure, Type N is the standard general-purpose pick.
Buy it or mix it
Pre-mixed bags or mix your own
Pre-blended mortar just needs water. Mixing from cement, lime and sand is cheaper at volume — and lets you dial in the exact type.
Small & mid jobs
Pre-mixed bags
Mason mix or mortar mix in a bag — add water and go. Consistent strength, no ratio math, easy cleanup.
Bigger builds
Mix on site
Buy Portland cement, hydrated lime and mason sand, and mix to the type ratio. Far cheaper once you're past a pallet of bags.
Get it right
What changes how much mortar you need
Two walls with the same block count can need different mortar. These four factors move the number most:
Joint thickness
Standard is 3/8 in. Go to 1/2 in and you use about 1.33× the mortar — thicker joints eat bags fast.
Unit size
Bigger blocks mean fewer joints per wall, so less mortar. Small brick has far more joint length per square foot.
Waste
10% is normal; go to 15% for cut-heavy work or hot, windy days when mortar sets before it's used.
Sand & water
Soft sand for laying, sharp for bedding. Over-watering weakens the joint — mix to a fatty, workable consistency.
Buy the waste the tool adds. Running out mid-course means a cold joint or a second trip — and a fresh batch that never quite matches the last.
Answers
Mortar calculator FAQs
How many bags of mortar per 100 block?
About 9 bags of 80-lb mortar (roughly 12 blocks per bag), or 10 once you add 10% for waste. In 60-lb bags it's about 13.
How many bags of mortar per 1,000 brick?
About 28 bags of 80-lb mortar — a bag lays roughly 36 modular bricks at a 3/8 in joint. Larger brick needs fewer bags.
How many blocks does a bag of mortar lay?
Roughly 12 standard 8×8×16 blocks per 80-lb bag, or about 8 per 60-lb bag, at a 3/8 in joint. Always check the bag's stated yield.
Type N or Type S mortar — which do I use?
Type N (1:1:6, 750 psi) for general above-grade brick and block. Type S (2:1:9, 1,800 psi) below grade or for load-bearing work like foundations and retaining walls.
How much sand and cement for mortar?
By type: Type N is 1 part cement : 1 lime : 6 sand. Overall the cement-to-sand ratio runs about 1:3 to 1:4.5. The tool's Mix tab gives the pounds for your job.
Should I buy 60-lb or 80-lb bags?
80-lb bags are better value and mean fewer bags to handle; 60-lb are lighter to lift and mix. The tool shows both counts side by side.
Does joint thickness change the mortar?
Yes. Standard is 3/8 in; a 1/2 in joint uses about 1.33× the mortar. Thicker joints add up quickly on a big wall.
How much extra mortar should I buy?
Add 10-15% for drops, premature setting and tooling the joints. It's built into the estimate — running short mid-course means a weak cold joint.