Grout Calculator

Last updated June 17, 2026 by our expert review team

Grout Coverage by Tile Size

Grout use is driven by tile size and joint width, not just area — 12×12 in tile with 1/8 in joints needs only ~16 lb per 100 sq ft, while 2×2 mosaic at the same joint needs several times more, because there's far more joint per square foot.

Pounds of sanded grout per 100 sq ft, at 5/16 in tile thickness:

Tile size	1/8 in joint	1/4 in joint
2×2 in	105.5 lb	210.9 lb
3×6 in	52.7 lb	105.5 lb
12×12 in	17.6 lb	35.2 lb
6×24 in	22 lb	43.9 lb
24×24 in	8.8 lb	17.6 lb

Per 100 sq ft, sanded grout, 5/16 in joint depth. Your tile thickness and grout type shift these; the calculator uses your exact inputs.

Expert Contributors

Creator

Hawkin

Certified Cost & Estimating Professional

Hawkin

Certified Cost & Estimating Professional

AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.

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Expert Review

Ehsan Ghazanfari

Licensed Structural Engineer

Ehsan Ghazanfari

Licensed Structural Engineer

FISE-certified structural engineer with 11+ years designing bridges, retaining walls, and foundations. MSc from Aalto University.

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Updated June 2026

How we verify our calculators

Pick your grout

Sanded, unsanded, or epoxy?

The choice is set mostly by joint width and the setting. Pick the wrong one and grout cracks, scratches the tile, or fails in wet areas.

Unsanded

≤ 1/8 in (3 mm)

Choose it if: Joints are 1/8 in or narrower, or the tile is polished/scratch-prone (glass, marble).

Smooth; can scratch soft tile if sanded

Sanded

1/8–1/2 in (3–12 mm)

Choose it if: Joints are 1/8 in or wider — sand resists shrinking and cracking in the wider gap.

Most floor tile; the default for wider joints

Epoxy

1/16–1/2 in (1.5–12 mm)

Choose it if: It's a wet, high-stain, or chemical area (showers, kitchens, commercial) and you want maximum durability.

Stain- and water-resistant; pricier and harder to work

Why small tile needs more grout: a large-format tile has little joint per square foot, while small mosaic has many more linear feet of joint, so it uses several times more grout. — Same area, same joint width — smaller tile packs in far more joint, so it uses much more grout.

Methodology

How the Grout Calculator Works

The calculator uses the Tile Council of North America joint-volume method: it finds the joint length per square foot from your tile size, multiplies by the joint cross-section (width × depth), and converts to weight with the grout's density. Smaller tile and wider joints both raise the total.

Grout density follows manufacturer data — sanded is denser than unsanded, and epoxy is denser still. See the TCNA Handbook for full installation guidance.

Formulas

Grout (lb) = [(L + W) ÷ (L × W)] × joint width × joint depth × density × (area × 144)

Density: sanded 0.1875, unsanded 0.165, epoxy 0.22 lb/in³

Bags = grout ÷ bag size (round up)

Quick Reference

≤ 1/8 in joint: unsanded
≥ 1/8 in joint: sanded
Wet / high-stain: epoxy
12×12 @ 1/8 in: ~16 lb / 100 ft²
Waste: add ~10%

Grout Examples

Floor: 12×12 Tile

120 sq ft, 1/8 in joints

23.2 lb1 bag0.19 lb / sq ft

Sanded grout suits the 1/8 in floor joint and resists cracking underfoot.

Subway Backsplash

30 sq ft, 1/16 in joints

6.1 lb1 bag0.20 lb / sq ft

Tight subway joints call for unsanded grout so the narrow gap packs cleanly.

Shower: Mosaic

45 sq ft, 1/8 in joints

49.9 lb5 bags1.11 lb / sq ft

Tiny mosaic = lots of joint per sq ft, so grout use is high. Epoxy adds water resistance in showers.

Avoid these

Grout Estimating Mistakes

Ignoring tile size

Area alone can't size grout. Small tile has far more joint per sq ft and needs much more grout.

Sanded grout in narrow joints

Use unsanded for joints 1/8 in and under, and on polished tile sand can scratch.

Forgetting joint depth

Grout fills the full tile thickness. A thicker tile means a deeper joint and more grout.

Buying exact, no waste

Add about 10% for mixing loss and repacking. Running out mid-job leaves color-matching headaches.

Grout Calculator FAQs

How much grout do I need for 100 square feet?

It depends most on tile size and joint width. For 12×12 in tile with 1/8 in joints, about 15–18 lb per 100 sq ft. Small mosaic at the same joint can need 3–4× as much because there is far more joint per square foot.

How much grout for a 12×12 tile floor?

A 120 sq ft floor of 12×12 in tile with 1/8 in joints needs about 23.2 lb of sanded grout (with 10% waste) — roughly 1 bag.

Should I use sanded or unsanded grout?

Use unsanded grout for joints 1/8 in and narrower, or for polished/scratch-prone tile like glass and marble. Use sanded grout for joints 1/8 in and wider, where the sand keeps the grout from shrinking and cracking.

Why does small tile need so much more grout?

Smaller tile means more linear feet of joint per square foot. A mosaic install can use several times the grout of a large-format floor at the same joint width — the 45 sq ft mosaic example needs about 49.9 lb.

Does joint width really matter that much?

Yes — it's the biggest lever after tile size. A 1/4 in joint uses roughly twice the grout of a 1/8 in joint on identical tile, because the joint cross-section doubles.

How many pounds is a bag of grout?

Sanded and unsanded grout commonly come in 10 lb and 25 lb bags; epoxy grout comes in smaller kits (often by the unit). Set your bag size in the calculator to get the bag count.

Should I add extra grout for waste?

Yes. Add about 10% for mixing loss, partial bags, and repacking joints. Tight mosaics and rough, porous tile can justify a bit more.

Need the tiles, thinset, and layout too? Use the tile calculator. Measuring the space first? Try the square footage calculator.

Important Disclaimer

These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.