Mortar Mix Ratio Converter
Look up mortar mix ratios for Type N, S, M, and O mortars.
Shows cement, lime, and sand proportions by type.
Select a mortar type to see its mix ratio and properties. Enter batch volume to calculate quantities.
Mix Ratio (by volume)
1 : 1 : 5.5 (cement : lime : sand)
Compressive strength: 750 psi (5.2 MPa)
Mortar is a mixture of cement, lime, and sand used to bond bricks, blocks, and stone in masonry construction. Different mortar types have different strength and flexibility characteristics suited to different applications.
Standard mortar types and their mix ratios (by volume):
| Type | Portland Cement | Hydrated Lime | Sand | Compressive Strength (psi) |
|---|---|---|---|---|
| M | 1 | 0.25 | 3-3.75 | 2,500 psi (17.2 MPa) |
| S | 1 | 0.5 | 4-4.5 | 1,800 psi (12.4 MPa) |
| N | 1 | 1 | 5-6 | 750 psi (5.2 MPa) |
| O | 1 | 2 | 8-9 | 350 psi (2.4 MPa) |
When to use each type:
- Type M (Mason): Highest strength. Used for below-grade applications, foundations, retaining walls, and driveways. Best where the mortar contacts the ground.
- Type S (Strong): High strength with good bonding. Used for exterior walls at or below grade, patios, chimneys, and areas subject to wind pressure. The most versatile exterior mortar.
- Type N (Normal): Medium strength, most commonly used mortar. Ideal for above-grade exterior walls, interior walls, and general-purpose masonry. Offers the best balance of strength, workability, and durability.
- Type O (Office): Lowest strength, very flexible. Used for interior, non-load-bearing walls and for re-pointing historic buildings where soft mortar is needed to protect old bricks.
The rule of thumb for remembering types: The letters M, S, N, O come from the words “MaSoN wOrk” when you take every other letter.
How lime affects mortar:
- More lime = softer, more flexible, easier to work with.
- Less lime = harder, stronger, but less forgiving.
- Lime improves water retention, which helps the mortar cure properly.
- Historic buildings used lime-only mortar (no Portland cement), which is much softer.
Mixing tips:
- Always measure by volume, not weight. One shovel of cement to the appropriate number of shovels of lime and sand.
- Mix dry ingredients first, then add water gradually until the mortar reaches a peanut-butter-like consistency.
- Mixed mortar stays workable for about 90 minutes. Do not add water to re-temper mortar after this time.
- Sand should be clean, well-graded masonry sand, not play sand or beach sand.