MasterTool

Mortar Calculator

Estimate bags of mortar from the number of bricks or blocks you are laying.

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What this tool does

Estimate bags of mortar from the number of bricks or blocks you are laying. Default coverage — about 37 standard blocks per 80 lb bag — is a published planning rate. For brick, set units per bag to about 100 (standard brick, ⅜ in joints). Always confirm against your mortar manufacturer's coverage table.

How to use the Mortar Calculator

  1. Enter or select unit being laid.
  2. Enter or select number of units to lay.
  3. Enter or select units laid per 80 lb bag.
  4. Read the calculated result; change any measurement to compare alternatives.

Formula

bags = ceil(units / units per bag); mixed mortar ≈ bags × 0.88 cu ft (80 lb bag yield)
unit
Unit being laid
count
Number of units to lay
perBag
Units laid per 80 lb bag

Default coverage — about 37 standard blocks per 80 lb bag — is a published planning rate. For brick, set units per bag to about 100 (standard brick, ⅜ in joints). Always confirm against your mortar manufacturer's coverage table.

Worked example

For mortar calculator, the following measurements illustrate the exact method: Unit being laid: block; Number of units to lay: 1000; Units laid per 80 lb bag: 37.

Inputs

  • Unit being laidConcrete block (CMU)
  • Number of units to lay1000
  • Units laid per 80 lb bag37

Result

  • Mortar bags (80 lb) to buy28
  • Mixed mortar volume24.64 cu ft
  • Units to lay1,000

Results explained

Mortar bags (80 lb) to buy
Mortar bags (80 lb) to buy from the formula above. Default coverage — about 37 standard blocks per 80 lb bag — is a published planning rate. For brick, set units per bag to about 100 (standard brick, ⅜ in joints). Always confirm against your mortar manufacturer's coverage table.
Mixed mortar volume
Mixed mortar volume from the formula above, expressed in cuft before metric conversion. Default coverage — about 37 standard blocks per 80 lb bag — is a published planning rate. For brick, set units per bag to about 100 (standard brick, ⅜ in joints). Always confirm against your mortar manufacturer's coverage table.
Units to lay
Units to lay from the formula above. Default coverage — about 37 standard blocks per 80 lb bag — is a published planning rate. For brick, set units per bag to about 100 (standard brick, ⅜ in joints). Always confirm against your mortar manufacturer's coverage table.

Frequently asked questions

At the planning rate of ~37 blocks per 80 lb bag, 100 blocks need 3 bags. The Mortar Calculator rounds up to whole bags.

Roughly 100 standard bricks per 80 lb bag with ⅜ in joints — set 'units per bag' to 100 when you switch the unit to brick.

Mortar is cement, lime, sand and water with no coarse aggregate — it bonds masonry units but is not structural fill. Never substitute it for concrete in footings.

Type N is standard above grade, Type S below grade and for higher strength, Type M for foundations and retaining work. The bag count is the same; the mix type is a strength choice.

Mix only what you can place in about 2 hours, add water sparingly, and retemper sparingly — over-wet mortar is weak mortar. Follow the bag instructions.