Mortar Calculator
Work out how many bags of mortar you need to lay brick or block: pick your unit type, enter the count (or get it from our brick and block calculators), and get 80 lb / 60 lb bag counts with a built-in waste factor.
From the brick or block calculator
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You might also need:Brick Calculator·Concrete Block Calculator
Mortar coverage math
coverage: 37 bricks or 13 blocks per 80 lb bag (⅜″ joints)
Coverage figures are the manufacturer-standard estimates for premixed mortar at ⅜-inch joints. Laying 500 modular bricks takes about 15 bags of 80 lb mortar with 10% waste; the same wall in 8×8×16 block (about 112 blocks) takes 10 bags.
Mortar types and strengths
| Type | Strength | Use |
|---|---|---|
| Type N | 750 psi | General purpose, above grade, veneer, chimneys |
| Type S | 1,800 psi | Below grade, retaining walls, foundations |
| Type M | 2,500 psi | Heavy loads, engineered masonry |
| Type O | 350 psi | Repointing soft historic brick, interior |
Mixing tips
- Small batches: mortar is only workable ~90 minutes. Two bags at a time is plenty for one mason.
- Consistency: aim for peanut-butter texture — it should cling to an upside-down trowel for a second.
- Weather matters: don't lay below 40°F without cold-weather practice, and dampen very dry units in summer so they don't suck the water out of the joint.
- Count your units first with the brick calculator or concrete block calculator.
Frequently asked questions
How many bricks or blocks does a bag of mortar lay?+
An 80 lb bag of premixed mortar lays roughly 37 modular bricks or 13 standard 8×8×16 concrete blocks with ⅜-inch joints. A 60 lb bag lays about 27 bricks or 10 blocks. Real coverage varies with joint size and how much you drop — order 10% extra.
What type of mortar should I use?+
Type N (750 psi) is the general-purpose choice for above-grade walls, brick veneer and chimneys. Type S (1,800 psi) is for below-grade, retaining walls and anywhere with soil contact. Type M (2,500 psi) is for heavy structural loads. Softer historic brick needs Type O to avoid damaging the units.
Should I buy premixed mortar or mix from cement and sand?+
Premixed bags (just add water) are simplest for small and mid-size jobs. For big jobs, site-mixing masonry cement with sand (1 part cement : 2¼–3 parts sand) is much cheaper — one 70 lb bag of masonry cement plus ~200 lb of sand makes about 2.4 cu ft of mortar.
How long does mortar take to set?+
Mortar becomes thumbprint-hard in 1–2 hours, holds the wall after 24–36 hours, and reaches full strength at 28 days like concrete. Only mix what you can use in about 90 minutes — retempering with extra water weakens it.
How thick should mortar joints be?+
Standard joints are ⅜ inch for both brick and block — the dimension unit sizes are designed around. Thicker joints weaken the wall and throw off coursing; anything over ½ inch means the units or footing are out of level.