Lime Mortar Proportions Calculator

Project Inputs

Measurement System

SI (mm, m, kg)

US/Imperial (in, ft, lb)

Wall length (m or ft)

Wall height (m or ft)

Wall thickness (m or ft)

Openings area (m² or ft²)

Unit length (mm or in)

Unit height (mm or in)

Unit width (mm or in)

Joint thickness (mm or in)

Assumed mortar fraction of masonry (%)

If unit/joint inputs are filled, this is adjusted.

Wastage allowance (%)

Dry to wet volume factor

Dry ingredients swell when mixed to wet; typical 1.3–1.4.

Bag size for powder materials (kg or lb)

Mix Type

Part A

Lime for pure/hydraulic; Cement for gauged.

Part B

Sand for 2-part mixes; Lime for gauged.

Part C

Sand for gauged; ignore for 2-part mixes.

Sand bulk density (kg/m³ or lb/ft³)

Lime apparent density (kg/m³ or lb/ft³)

Cement bulk density (kg/m³ or lb/ft³)

Results

0 m³

Masonry Volume

0 m³

Wet Mortar Needed

0 m³

Dry Ingredients Volume

0 t

Sand Tonnage

Item	Volume	Mass	Bag Count	Notes
Click Calculate to populate results.

Units show as SI defaults. If Imperial selected, inputs convert, but outputs normalize to SI with equivalent Imperial notes in table.

Example Mixes

Application	Type	Nominal Ratio	Badge
Historic brickwork repointing	Pure Lime	1 : 2.5 (lime : sand)	Soft
General stone masonry	Hydraulic Lime NHL 3.5	1 : 2.5 (lime : sand)	Moderate
Exposed external walls	Hydraulic Lime NHL 5	1 : 2.5–3 (lime : sand)	Stronger
Gauged repair mortar	Cement-Lime-Sand	1 : 1 : 6	Gauged

Formula Used

1) Masonry volume: V_masonry = (Length × Height × Thickness) − Openings

2) Mortar wet volume: V_wet = V_masonry × f_mortar, where f_mortar is the mortar fraction (e.g., 0.275). When unit and joint sizes are supplied, the fraction is adjusted by estimating joint volume per unit.

3) Dry ingredients volume: V_dry = V_wet × Dry/Wet Factor

4) Component split by ratio: For a 2-part mix lime:sand = a:b: V_lime = V_dry × a/(a+b), V_sand = V_dry × b/(a+b). For a 3-part mix cement:lime:sand = a:b:c, split by a+b+c.

5) Masses and bags: m = ρ × V. Bag count = m / bagSize. Sand tonnage = m_sand / 1000 (t).

How to Use This Calculator

Select your measurement system.
Enter wall geometry, openings, and unit/joint dimensions.
Choose a mix type and set the ratio parts.
Set wastage, dry–wet factor, and bag size as needed.
Click Calculate to see volumes, masses, and bag counts.
Export results as CSV or PDF using the top buttons.

FAQs

Typical masonry uses 25–30% mortar by volume. Start with 27.5% and adjust based on unit size and joint thickness for your project.

Pure lime suits soft historic masonry. Hydraulic lime (NHL 2/3.5/5) gains strength faster and handles exposure better. Match strength to the masonry, not stronger than the units.

Pure/hydraulic lime often ranges 1:2 to 1:3 (lime:sand). A common gauged mix is 1:1:6 (cement:lime:sand). Always confirm with local standards and conservation guidance.

Dry ingredients yield more volume than the resulting paste. Multiplying wet volume by 1.3–1.4 approximates required loose volumes before mixing.

Inputs accept Imperial. Core outputs list SI units with an Imperial note per line for quick reference and ordering.

Example Data Table

Scenario	Mix	Ratio	Dry Factor	Mortar %	Bag Size
Interior brick repointing	Pure Lime	1 : 2.5	1.33	26	25 kg
External stone wall	NHL 3.5	1 : 2.5	1.35	28	25 kg
Parapet coping	NHL 5	1 : 3	1.35	30	25 kg
Repair patch	Gauged	1 : 1 : 6	1.33	27.5	25 kg

Disclaimer: This tool provides planning estimates. Verify with project specifications, standards, and material suppliers before ordering.

Project Inputs

Results

Example Mixes

Formula Used

How to Use This Calculator

FAQs

What mortar fraction should I use?

Pure lime or hydraulic lime?

What ratios are common?

How is dry–wet factor used?

Can I switch to Imperial outputs?

Example Data Table

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