Mortar Calculator
Mason mix is estimated per unit laid, not per cubic foot of joint, because the bag itself is sold with a published yield. This calculator takes the number of standard concrete blocks you are laying and returns the 80 lb bags to buy, using the yield QUIKRETE prints on the data sheet.
How it works
One 80 lb bag of mason mix lays up to 13 standard 8×8×16 in blocks. That is 6.15 lb of dry mix per block, which is the whole calculation — everything else is rounding.
The same bag lays up to 37 standard bricks, or 2.16 lb per brick. A brick takes less mortar than a block because it is a smaller unit, though a brick wall has far more joints per square foot, so the two roughly converge by area.
Bags round up, since the yard sells whole bags. The calculator also reports the total mix weight so you can tell whether the order is a trunk load or a pallet: 180 blocks is 14 bags and 1,120 lb.
Formula: Bags = blocks ÷ 13 blocks per 80 lb bag, rounded up to whole bags
Measuring on site
- Count the blocks first. If you do not have a count, run the wall through the cinder block calculator — it returns the number this page needs.
- Enter the blocks you will actually lay, not the count inflated for breakage. A block that cracks on site never gets mortared, so waste blocks do not consume mix.
- The published yield is a per-unit figure with no joint thickness attached to it, so it reflects ordinary practice rather than a specific joint. Tooling unusually thick joints, or parging a face, uses more. Filling cores is a different job entirely: that is grout or core-fill, not mason mix, and this calculator does not cover it.
Waste and what it covers
The manufacturer says a bag lays 'up to' 13 blocks, which makes the yield an optimistic ceiling rather than a field average, so no extra waste factor is layered on top of it here. What comes out of that ceiling in practice is mortar stiffening on the board, mix dropped off the trowel and whatever is left in the mixer. Rounding up to whole bags already covers a small job — 113 blocks needs 8.7 bags and buys 9 — but on anything above a few hundred blocks an extra bag is cheap next to a stopped wall.
| Blocks | 80 lb bags | Total mix weight |
|---|---|---|
| 50 | 4 | 320 lb |
| 100 | 8 | 640 lb |
| 113 (a 10 × 10 ft wall) | 9 | 720 lb |
| 180 (a 20 × 8 ft wall) | 14 | 1,120 lb |
| 360 (a 40 × 8 ft wall) | 28 | 2,240 lb |
Questions
- How many bags of mortar per block?
- One 80 lb bag per 13 blocks, which is 6.15 lb of mix for each block. Per-block figures are only useful for scaling, though — you buy whole bags, so the practical answer is always the rounded-up total for the wall.
- How many bags of mortar do I need for 100 blocks?
- 8 bags. 100 divided by 13 is 7.7, and part bags are not sold, so the order is 8 bags and 640 lb of mix. The leftover is real: you have paid for roughly 4 blocks' worth of capacity you will not use.
- How much mortar for a 10 x 10 block wall?
- 9 bags. A 10 × 10 ft wall comes to 113 blocks by area, and 113 divided by 13 is 8.7. That is 720 lb of mason mix. Feed this calculator the blocks that get laid, not the number you order: the block calculator asks for more than 113 there, because it counts the whole block you take off the pallet to cut a course end and adds the breakage allowance on top. Neither the offcut nor the spare ever meets a trowel.
- How many bricks will an 80 lb bag of mortar lay?
- Up to 37 standard bricks, against 13 standard blocks, from the same data sheet. That is 2.16 lb of mix per brick. This calculator is built around the block figure; for a brick job, divide your brick count by 37.
Sources
- QUIKRETE — Mason Mix data sheet (Product No. 1136)“Each 80 lb (36.2 kg) bag of QUIKRETE® Mason Mix will lay up to 37 standard bricks or 13 standard (8 in by 8 in by 16 in) blocks.”
Figures and sources last checked by The BuilderTally Team in August 2026.