Skip to main content
Shops Free Pro Features Available

Grout and Thinset Calculator

Calculate thinset mortar and grout quantities based on tile size, joint width, and trowel notch size

Free grout and thinset calculator for tile installers, contractors, and DIY homeowners who need to know how much mortar and grout to buy before starting a tile job. Enter the floor or wall area, tile size, grout joint width, and trowel notch size. The calculator returns the number of bags of thinset mortar, pounds of grout, and coverage per bag based on the mortar bed thickness created by your trowel selection. Supports sanded grout, unsanded grout, and epoxy grout. Includes back-buttering adjustments for large-format tiles and natural stone.

Pro Tip: Trowel notch size is the single biggest factor in thinset consumption, and most homeowners pick the wrong one. A 1/4" x 1/4" square-notch trowel uses roughly half the mortar per square foot compared to a 1/2" x 1/2" square-notch trowel. The TCNA Handbook specifies minimum trowel sizes based on tile size: 1/4" x 1/4" for tiles up to 8 inches, 1/4" x 3/8" for 8-15 inch tiles, and 1/2" x 1/2" for tiles 16 inches and larger. Using a trowel that is too small risks hollow spots and tile lippage. Using one that is too large wastes mortar and can cause ooze-up into the grout joints.

Calculate flooring material quantities for non-tile floors

Flooring Material Calculator →

PREVIEW All Pro features are currently free for a limited time. No license key required.

Grout & Thinset Calculator
Pop Out

How It Works

  1. Enter Tile Area

    Input the total area to be tiled in square feet. For floors, this is the room area minus any permanent fixtures (cabinets, islands). For walls, measure each wall section separately, subtracting windows and niches. Add 10% for cuts and waste on the tile quantity itself.

  2. Set Tile and Joint Dimensions

    Enter the tile size (length and width), grout joint width, and tile thickness. Common joint widths are 1/16 inch for rectified tile, 1/8 inch for standard floor tile, and 3/16 to 1/4 inch for handmade or rustic tile. The calculator uses these dimensions to compute the grout volume per square foot.

  3. Select Trowel Size and Mortar Type

    Choose your trowel notch size (1/4" x 1/4", 1/4" x 3/8", or 1/2" x 1/2") and mortar type (unmodified thinset, modified thinset, or large-format tile mortar). The trowel size determines the mortar bed thickness, which directly controls how many square feet each bag covers. Select whether you are back-buttering large-format or natural stone tiles.

  4. Review Material Quantities

    The output shows the number of 50-lb bags of thinset mortar, pounds of grout (sanded, unsanded, or epoxy), coverage per bag at your trowel size, and the total mortar bed volume. A cost estimate is included if you enter the price per bag. The calculator also flags if your trowel selection is too small or too large for the tile size.

Built For

  • Tile installers preparing material orders for residential bathroom and kitchen remodels
  • General contractors estimating thinset and grout costs for commercial tenant improvement projects
  • DIY homeowners ordering materials for a first-time tile backsplash or shower surround
  • Flooring supply houses helping customers calculate quantities at the counter
  • Property managers budgeting tile repair materials for maintenance crews

Assumptions

  • Thinset coverage per bag is based on manufacturer-published rates for the selected trowel notch size.
  • Grout volume calculation assumes uniform joint width and depth equal to tile thickness.
  • Back-buttering adds 15-25% to thinset consumption depending on tile size and texture.
  • Waste factor of 10% is applied to both thinset and grout quantities.

Limitations

  • Does not calculate substrate preparation materials (cement backer board, uncoupling membrane, waterproofing).
  • Does not model mosaic sheet tile installations where joint spacing varies within the sheet.
  • Does not account for mortar bed thickness variations caused by uneven substrates.
  • Does not calculate tile quantity or cut waste. Enter the tile area net of waste for accurate mortar estimates.

References

  • TCNA Handbook for Ceramic, Glass, and Stone Tile Installation (Current Edition)
  • ANSI A108/A118/A136 - American National Standard Specifications for Tile Installation
  • Tile Council of North America - Trowel Size Selection Guide
  • ASTM C1472 - Standard Guide for Calculating Installed Thin-Set Tile Coverage

Frequently Asked Questions

The TCNA Handbook provides minimum trowel sizes based on tile surface area. For mosaic tiles up to 4 inches, use a 3/16" x 1/4" V-notch. For tiles 4-8 inches, use a 1/4" x 1/4" square-notch. For tiles 8-15 inches, use a 1/4" x 3/8" square-notch. For large-format tiles 16 inches and larger, use a 1/2" x 1/2" square-notch. The goal is to achieve a minimum 80% mortar coverage on floor tiles (95% on wet areas and exteriors). After setting a tile, peel it up and check the back: if the trowel ridges have fully collapsed and coverage is even, the trowel size is correct.
Unmodified (dry-set) thinset is a Portland cement and sand mixture that cures by hydration and bonds mechanically to porous surfaces. Modified thinset has polymers (latex or acrylic) added that improve flexibility, bond strength, and water resistance. Use unmodified thinset over uncoupling membranes (like Schluter DITRA) because the membrane needs the mortar to cure by drying, and modified thinset cures too slowly when sandwiched between two impervious surfaces. Use modified thinset for direct bond to concrete, cement backer board, plywood, or any substrate where the mortar can cure from one side. Always check the membrane manufacturer's recommendation.
Use sanded grout for joints 1/8 inch and wider. The sand aggregate fills the joint volume and prevents cracking as the grout cures and shrinks. Use unsanded grout for joints narrower than 1/8 inch, typically with rectified (precision-cut) porcelain or glass tile. Unsanded grout is also preferred for polished marble and soft natural stone because sand particles can scratch the tile surface during grouting. For joints wider than 3/8 inch, use a heavily sanded or "wide joint" grout formulated for large gaps. Epoxy grout can be used at any joint width and provides superior stain and chemical resistance.
Back-buttering means applying a thin layer of thinset to the back of the tile in addition to the troweled mortar bed on the substrate. It is required for tiles larger than 15 inches on any side, all natural stone tiles, and any installation where ANSI A108 requires 95% mortar coverage (wet areas, exterior, and tiles over 15 inches). The back-butter layer fills the texture on the tile back and ensures full contact with the mortar ridges from the substrate. This process increases thinset consumption by approximately 15-25%, and the calculator adds this to the material estimate when back-buttering is selected.
Epoxy grout costs roughly 3-5 times more per pound than standard cement-based grout. A 10-lb unit of epoxy grout typically costs $30-$50, while a 10-lb bag of sanded cement grout costs $8-$15. However, epoxy grout never needs sealing, resists staining permanently, does not absorb water, and handles chemical exposure far better than cement grout. For high-traffic commercial kitchens, food service areas, showers, and pools, the extra cost is justified by the elimination of ongoing maintenance and resealing. For a standard residential floor, cement grout with periodic sealing is usually the more cost-effective choice.
Disclaimer: This calculator provides estimates for material planning. Actual quantities may vary based on room geometry, waste, and installation method. Always order extra material from the same production lot. Consult manufacturer guidelines for specific products. ToolGrit is not responsible for material shortages or overages.

Learn More

Shops

Thinset and Grout: Trowel Selection, Coverage Rates, and Material Types

TCNA trowel size guidelines, modified vs unmodified thinset, sanded vs unsanded vs epoxy grout, back-buttering large format tile, and substrate requirements.

Read Guide →

Related Tools

Shops & Outbuildings Live

Shop Heater BTU Sizing Calculator

Calculate the exact BTU output your shop or garage heater needs. Factors in wall R-values, ceiling insulation, slab edge loss, overhead door infiltration, and air changes per hour to size propane, natural gas, and electric heaters correctly.

Launch Tool →
Shops & Outbuildings Live

Overhead Door Infiltration Loss Calculator

Calculate heat loss through overhead doors in shops, garages, and warehouses. Compares open-door vs closed-door losses, seal condition impact, and annual cost of infiltration with payback on door seals and high-speed doors.

Launch Tool →
Shops & Outbuildings Live

Long-Run Voltage Drop Calculator

Calculate voltage drop for long wire runs to detached shops, barns, garages, and outbuildings. Compares copper vs aluminum, shows motor starting voltage impact, and recommends the right wire size for your distance and load.

Launch Tool →