Grout Calculator — Free Tile Grout Estimator
Grout quantity depends on four variables: tile size, joint width, tile thickness, and total area. This calculator supports all three grout types — sanded, unsanded, and epoxy — and applies the correct density constant for each so the bag count is always accurate. Results are brand-agnostic: the formula is derived from the TCNA Handbook and ANSI A108.10, not from any manufacturer's coverage chart.
A grout calculator estimates the weight of grout needed by computing the total joint volume — a function of tile size, joint width, and tile thickness — multiplying by grout density (sanded 104 lb/ft³, unsanded 86 lb/ft³, epoxy 100 lb/ft³), and adding a waste buffer (10–20%). The result converts directly to whole-bag counts.
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Grout Calculator
TCNA Handbook formula · ANSI A108.10
Area
Total tiled surface area. Need to measure first? Use the square footage calculator.
Tile Dimensions
Width of one tile (the shorter side for rectangular tiles).
Length of one tile (the longer side for rectangular tiles).
Standard porcelain is about 3/8 inch (9.5 mm). Joint depth equals tile thickness.
Grout Settings
Common residential range: 1/16" – 3/8". Most floor tile sits at 3/16".
Sanded for joints ≥ 1/8", unsanded for joints < 1/8", epoxy for showers and chemical exposure.
Choose the bag size you plan to buy. The calculator rounds up to whole bags.
10% straight lay · 15% showers, herringbone, diagonal · 20% mosaic and irregular stone.
Enter your area, tile dimensions, and joint width to see grout requirements.
All Three Grout Types
Sanded, unsanded, and epoxy — each with the correct density constant.
TCNA Handbook Formula
Joint volume computed per TCNA specs with tile thickness as joint depth.
PE-Reviewed Formula
Verified by Alex Rivera, PE against ANSI A108.10 and TCNA Handbook.
This calculator is an educational estimation tool. For commercial tile projects or projects requiring code compliance, consult a licensed tile contractor.
Section 01
How to Use the Grout Calculator
If you have not measured yet, use the square footage calculator first to get a clean number, then return here to run the grout estimate.
- Enter the total tiled surface area in square feet.
- Enter tile width and height in inches from the box label.
- Enter tile thickness — standard porcelain is 3/8". Joint depth equals tile thickness.
- Set grout joint width. Most floor tile uses 3/16". Joints under 1/8" require unsanded; 1/8" and wider require sanded.
- Select grout type (sanded, unsanded, epoxy) and bag size.
- Set waste factor: 10% straight lay, 15% showers or diagonal, 20% mosaic.
- Click Calculate Grout Now. The result shows bags, total weight, and coverage per bag.
Section 02
The Grout Formula Explained
The TCNA Handbook formula computes grout volume by treating each joint as a rectangular channel with width equal to the joint width and depth equal to the tile thickness.
JV = 2 × (L + W) / ((L + J) × (W + J)) × J × D × 144
Weight = JV × Area / 1728 × Density × (1 + Waste)
Bags = ⌈Weight / BagSize⌉
JV = joint volume (cu in / sq ft) · L = tile length (in) · W = tile width (in)
J = joint width (in) · D = tile thickness (in) · Density = lb/ft³
Sanded 104 lb/ft³ · Unsanded 86 lb/ft³ · Epoxy 100 lb/ft³
Section 03
Which Type of Grout Do You Need?
Joint width is the primary selection criterion. ANSI A108.10 sets a 1/16" minimumjoint width for calibrated tile. The 1/8" threshold determines whether to use sanded or unsanded grout.
| Type | Joint Range | Density | Best For | Avoid On |
|---|---|---|---|---|
| Sanded | 1/8" – 1/2" (3–12.7 mm) | 104 lb/ft³ | Floor tile, most wall tile, kitchen backsplash | Polished stone, glass tile (scratches surface) |
| Unsanded | 1/16" – 1/8" (1.6–3 mm) | 86 lb/ft³ | Polished stone, marble, glass tile, tight joints | Joints wider than 1/8" — will shrink and crack |
| Epoxy | 1/16" – 1/2" | 100 lb/ft³ | Showers, steam rooms, food-service areas, chemical exposure | Exterior freeze–thaw; requires more prep and skill |
For a wall installation that bonds tile to substrate underneath, see the thinset calculator for adhesive coverage.
Section 04
Grout Joint Width Guide
Joint width controls both the visual character of the installation and the amount of grout required. ANSI A108.10 establishes 1/16" as the minimum for calibrated tile and 3/32" for uncalibrated tile.
1/16"
1.6 mm
Glass tile, rectified porcelain
Unsanded1/8"
3.2 mm
Subway tile, polished stone
Unsanded3/16"
4.8 mm
Most floor tile (default)
Sanded1/4"
6.4 mm
Rustic stone, saltillo
SandedSection 05
Choosing the Right Waste Factor
The waste factor accounts for two sources of loss: mixing waste (grout mixed but not applied) and application waste (grout lost in cuts and joints that need correction). Running short mid-job forces a new batch, and color matching between batches is unreliable.
Standard Waste Factor (10%)
Use 10% for straightforward grid-pattern installations on flat, prepared substrates. This is the industry default and covers normal mixing loss and minor joint corrections for field tile laid in a standard running-bond or square pattern.
Condition-Based Waste Factors
Increase to 15% for wet areas (showers, steam rooms) where extra mixing batches are common, or for floors with many cut edges around fixtures. Use 20% for irregular substrates, natural stone with variable joint widths, or any project where the grout color must match an existing installation exactly.
Pattern-Specific Waste (Herringbone, Diagonal, Mosaic)
Herringbone and 45-degree diagonal patterns generate significantly more cut pieces along perimeters, increasing both tile and grout waste. Mosaic sheets have high joint density — the volume of grout per square foot is much greater than large-format tile, and mixing waste is amplified because smaller batches are less efficient. Budget 20% for all three patterns.
| Pattern / Application | Waste Factor | Notes |
|---|---|---|
| Straight (grid) | 10% | Cuts only at room perimeter. |
| Diagonal / 45° | 15% | Triangular off-cuts at all four perimeters. |
| Herringbone | 15–20% | Staggered cuts plus higher breakage risk. |
| Mosaic sheets | 20% | High joint density; mixing waste is significant. |
| Irregular natural stone | 20% | Variable joint widths; verify with spec. |
Section 06
Grout Coverage by Tile Size
Smaller tiles require more grout per square foot because they have more joint perimeter per unit area. The table below gives reference coverage ranges — use the calculator above for the precise figure for your tile and joint combination.
| Tile Size | Joint Width | Grout per 100 sq ft | Notes |
|---|---|---|---|
| Mosaic 2×2 in | 1/8" | 8–12 lb / 100 sq ft | High joint density. |
| Subway 3×6 in | 1/16" | 3–4 lb / 100 sq ft | Unsanded standard. |
| Field 6×6 in | 1/8" | 3–4 lb / 100 sq ft | Unsanded standard. |
| Standard 12×12 in | 1/8" | 1–2 lb / 100 sq ft | Unsanded at ≤ 1/8". |
| Plank 12×24 in | 3/16" | 1–1.5 lb / 100 sq ft | Sanded. |
| Large-format 24×48 in | 3/16" | 1–1.5 lb / 100 sq ft | Sanded; leveling system recommended. |
Section 07
Room-by-Room Grout Guide
Bathroom Floor
Tile: 12×12 porcelain
Joint: 3/16"
Grout type: Sanded
Waste factor: 10%
Standard straight-lay. Check for radiant heat sleeves before grouting.
Shower Walls
Tile: 3×6 subway
Joint: 1/16"
Grout type: Unsanded
Waste factor: 15%
Use white unsanded for polished-finish subway. Consider epoxy for steam showers.
Kitchen Backsplash
Tile: 3×12 subway
Joint: 1/16"
Grout type: Unsanded
Waste factor: 10%
Seal grout within 72 hours of cure. Epoxy grout near cooktop for grease resistance.
Large-Format Floor
Tile: 24×24 porcelain
Joint: 3/16"
Grout type: Sanded
Waste factor: 10%
Use a tile leveling system. Larger tiles need a flatter substrate for this joint width.
Mosaic Shower Floor
Tile: 2×2 mosaic
Joint: 1/8"
Grout type: Unsanded or epoxy
Waste factor: 20%
High joint density — verify grout coverage from sheet manufacturer spec.
Outdoor Patio
Tile: 12×12 slate
Joint: 3/8"
Grout type: Sanded
Waste factor: 15%
Use a freeze–thaw rated sanded grout. Avoid epoxy in exterior applications.
Section 08
Do You Need Grout Sealer?
Cement-based grout (sanded and unsanded) is porous and absorbs water and stain without sealer. Epoxy grout is non-porous and does not require sealing.
✓
Sanded grout
Yes — seal after 72 h cure
✓
Unsanded grout
Yes — seal after 72 h cure
✗
Epoxy grout
No — non-porous
A standard penetrating grout sealer covers approximately 50 sq ft per quart. For a 100 sq ft bathroom floor, budget 2 quarts. Reapply every 1–2 years in wet areas.
Industry Standards Referenced
Section 09
Grout Calculator FAQ
Reviews: conversion calculators · 22 calculators reviewed
Rachel Torres is a construction education specialist holding an M.Ed. and NCCER Master Trainer certification (#MT-2018-4492). With 14 years bridging field engineering at Kiewit Infrastructure and classroom instruction, she writes CalcSummit's conversion calculators, educational guides, and glossary content to NCCER and ICC curriculum standards. She developed the 'Construction Math Made Simple' course used by ACTE member programs.
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