Tile Grout Calculator
Pounds of grout from tile size, joint width and tiled area — calculated from the actual volume of the joints, then converted to bags.
Result
| Grout needed | |
| Joint length per ft² | |
| 10-lb bags | |
| 25-lb bags |
Units & conversions used
Tile dimensions and joint width are in inches; area is in ft². Metric inputs are converted first: 1 m² = 10.7639 ft², 1 cm = 0.3937 in, 10 mm = 0.3937 in. Grout is sold in 10-lb boxes and 25-lb bags in the US.
Formula & source
Grout volume per ft² = joint length × joint width × tile thickness (in³)
Weight = volume × 0.069 lb/in³ × area (ft²)
Source: this is the joint-volume method — the grout in a floor occupies the grid of joints, so its amount follows from joint length, width and depth. The 0.069 lb/in³ factor is the stated assumption for mixed cementitious grout density used by this calculator. As a cross-check, it lands in line with commonly published manufacturer coverage charts: at the worked example's rate, one 25-lb bag covers about 320 ft² of 12×12 tile at 1/8 in joints, which matches typical chart values for sanded grout. Your product's own coverage chart always governs.
Worked example (you can verify by hand)
Input: 100 ft² of 12 in × 12 in tile, 1/8 in (0.125) joints, 3/8 in (0.375) thick tile.
- Joint length per ft²: 144 × (12 + 12) ÷ (12 × 12) = 24 in
- Joint volume per ft²: 24 × 0.125 × 0.375 = 1.125 in³
- Weight per ft²: 1.125 × 0.069 = 0.0776 lb
- For 100 ft²: 0.0776 × 100 = 7.76 lb → one bag covers it
Expected output: 7.76 lb of grout; buy 1 × 25-lb bag (a 10-lb bag is also enough).
Limitations — what this cannot do
- Assumes joints are filled to full tile depth on a uniform grid. Cushioned or beveled tile edges hold more grout than rectified edges; handmade and rustic tile can use noticeably more.
- The density factor is for cementitious grout. Epoxy and pre-mixed (single-component) grouts have different densities and are sold by different units — use their charts instead.
- Real-world consumption also depends on mixing waste, wash-water practice and how much grout is left in the bucket; buying one full bag beyond the estimate for a multi-room job is common practice.
- Buy all grout for a continuous area from the same product lot and mix whole bags where possible — shade varies slightly between lots and between partial mixes.
FAQ
Sanded or unsanded grout — which do I need?
The usual rule: sanded grout for joints 1/8 in and wider (the sand resists shrinkage and cracking), unsanded for narrower joints and for scratch-sensitive tile like polished marble or glass. Many modern single-component and high-performance grouts blur this line — the bag's instructions govern.
Why does the calculator ask for tile thickness?
Because grout fills a volume, not a surface. A 3/8 in floor tile has joints half again as deep as a 1/4 in wall tile of the same size, and needs roughly 50% more grout per square foot — calculators that ignore depth under-order for thick tile.
How much does grout cost?
Cementitious grout commonly sells in the $10–$30 range for a 10-lb box or 25-lb bag depending on brand and type (2025–2026); high-performance and epoxy grouts commonly cost several times that per unit. Grout is a small share of a tile job's budget — under-buying and running out mid-room costs more in delay than a spare bag.
Can I save leftover grout for touch-ups later?
Dry powder keeps about a year if the bag stays sealed and dry; once mixed with water it cannot be stored. Keeping a small sealed bag from the same lot is the best way to guarantee a color match for future repairs.