Grout Calculator
Work out how much grout a tiled area needs, by weight.
Last reviewed September 19, 2026
Result
Buy 6 lb kilogramsEstimate
Ten per cent is the default. Grout is mixed in batches and what is left in the bucket when it goes off cannot be revived, so the allowance covers the batch you throw away rather than any loss in the joint itself.
- Grout volume
- 1.536287 L
- Total length of joint
- 200 ft
https://calcgallery.com/flooring-tile/grout-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use it
- Enter the tiled area, or take it from the tile calculator.
- Enter the tile length and width. Long thin tiles need much more grout than square ones.
- Set the joint width to match your spacers, and the joint depth to the tile thickness.
- Read the weight of grout, and buy the next bag size up.
How it is calculated
Grout fills the joints, so the calculation is the length of joint in the area, times the cross section of the joint:
joint length = area × (tile length + tile width) ÷ (tile length × tile width)
volume = joint length × joint width × joint depth
weight = volume × density × (1 + waste)The first line is the part worth understanding. Each tile is surrounded by joint, but every joint is shared between two tiles, so each tile is counted as owning half the joint on each of its four sides. That works out to (l + w) / (l × w) of joint per unit of area.
For 300 mm square tiles that is 6.67 m of joint for every square metre. The tile size is doing all the work here: joint width and depth matter, but nothing changes the answer like halving the tile.
Practical tips
Measure the joint you will actually have. Spacers set the minimum. Hand-cut or rustic tiles often end up with wider joints than the spacers suggest, and on a large floor that difference adds up to a whole extra bag.
Buy it all at once, from one batch. Cement grout is pigmented, and two bags from different dye lots can be visibly different once dry. Running out halfway across a floor is the one mistake you cannot fix without regrouting.
Mix smaller batches than you think. Grout starts going off in the bucket well before you have finished spreading it, and working it after it has begun to stiffen gives a patchy, weak joint. Mixing half a bag twice beats mixing a whole bag once.
Seal porous tile first. Unglazed stone, terracotta and some porcelain will absorb pigment from the grout and stain permanently. A test tile and ten minutes will tell you.
Do not grout over an empty joint. If the adhesive has slumped into the joint, rake it out before grouting. A joint that is only half depth looks the same on the day and cracks out within a year.
With your numbers
- Joint length = 100 ft² of 12 in × 12 in tile = 200 ft of joint
- Volume = that × 0.125 in wide × 0.3125 in deep = 1.536 L
- Grout = that × density, plus 10% waste, rounded up to 6 lb
Quick reference
Ten per cent is the default. Grout is mixed in batches and what is left in the bucket when it goes off cannot be revived, so the allowance covers the batch you throw away rather than any loss in the joint itself.
| Job | Grout needed |
|---|---|
| 10 m², 300 mm tile, 3 mm joint | 2.9 kg |
| 20 m², 300 mm tile, 3 mm joint | 5.7 kg |
| 10 m², 600 mm tile, 3 mm joint | 1.8 kg |
| 5 m² of 150 mm wall tile | 1.5 kg |
| 100 ft², 12 in tile, 1/8 in joint | 6 lb |
| 200 ft², 12 in tile, 1/8 in joint | 12 lb |
| 100 ft², 18 in tile, 3/16 in joint | 7.2 lb |
| 50 ft² of subway tile | 3.6 lb |
Common questions
- How much grout do I need for 10 square metres?
- About 2.9 kg for 300 mm tiles with a 3 mm joint 8 mm deep, including a 10 per cent allowance. Halve the tile size and you roughly double the grout; double the tile size and you roughly halve it.
- Why does tile size change the grout so much?
- Because grout fills the joints, and smaller tiles mean far more joint in the same area. Ten square metres of 300 mm tile has about 67 m of joint. The same area in 100 mm mosaic has about 200 m. The area is identical and the grout is three times as much.
- What joint depth should I use?
- The tile thickness, in almost every case. Joints are grouted full depth, so a 10 mm tile gives a 10 mm deep joint. If you are grouting over an existing bed that has partly filled the joint, measure what is actually open rather than the tile.
- Should I use sanded or unsanded grout?
- Sanded grout for joints wider than about 3 mm, or 1/8 in, because it resists shrinking and cracking. Unsanded for narrower joints, and for polished stone or glass that sand would scratch. The quantity is much the same either way; the choice is about the joint, not the volume.
- How much extra should I buy?
- The 10 per cent default covers what sets in the bucket rather than losses in the joint. Buy in whole bags and round up generously: running out mid wall means a visible colour change where the new batch starts, and dye lots do not always match.
- Does this cover epoxy grout?
- The volume does, but the weight does not. Epoxy grout has a different density and comes in fixed kit sizes, so work from the volume figure and the manufacturer's coverage chart instead.