Grout Calculator UK: How Much Tile Grout Do I Need?
Enter your area, tile size, tile thickness and joint width. This grout calculator then shows grout per m², total kilograms, bags and cost for cement or epoxy grout.
More free UK building calculators
Grout comes last, so these calculators cover the tiles, adhesive and groundwork that come first.
Tiles per m², boxes and wastage for floors and walls.
Adhesive per m² and 20 kg bags by trowel notch.
Cubic metres, bags, cement and ballast for slabs and footings.
Bricks per m², mortar and cost for any wall.
Concrete, breeze and aircrete blocks, with mortar and cost.
MOT Type 1, ballast, sand and gravel in tonnes and bulk bags.
Rise, going, pitch and stringer length, with Part K checks.
Tonnage, coverage and driveway cost per m².
Why guessing your grout quantity backfires
Picture this. You finish grouting a shower wall on Saturday with two rows still bare, then buy another bag.
A week later, those final rows look noticeably darker. Grout colour depends on the production batch, the water quantity and the drying conditions. Separate mixes rarely match perfectly.
Grout costs very little compared with tiles. However, a patchy finish spoils the entire wall, and removing cured grout takes hours. So how much should you actually buy?
Our rule: buy enough grout for the whole job in one go, from one batch. Measure the water for every mix, so each one dries to the same shade.
How much grout per m² for floor tiles?
Large 600 × 600 mm porcelain with 3 mm joints requires only 0.16 kg per m². Smaller 300 × 300 mm tiles require 0.26 kg, because they contain twice the joint length.
How much grout for wall tiles and mosaics?
Metro tiles with 2 mm joints require approximately 0.30 kg per m². Small 25 mm mosaics require around 1 kg per m², roughly six times more than large floor tiles.
How to use the tile grout calculator
You need the area plus three tile measurements. Most manufacturers print all three on the box label.
- Enter the area. Type length and width, or a total area in square metres or square feet.
- Choose a common tile size. The preset list fills the length, width and thickness for you.
- Check the tile thickness. Thickness determines the joint depth, so it significantly affects the result.
- Set the joint width. Floors often use 3 mm and walls 2 mm. Rectified porcelain can go narrower.
- Pick cement or epoxy grout. The density updates automatically, or you can enter the manufacturer’s figure.
- Add the bag size, wastage and price. The calculator rounds up to complete bags and totals the cost.
Planning the whole job? Count the tiles with our tile calculator and work out the bedding with the tile adhesive calculator. Then come back here for the grout.
Grout calculator formula: how to work out grout per m²
Grout fills the gaps between tiles, so the quantity depends entirely on joint volume. Smaller tiles create additional joints per square metre, and thicker tiles create deeper joints. Both increase the total.
Grout per m² for popular UK tile sizes
| Tile size and thickness | Joint | Joint length per m² | Grout per m² |
|---|---|---|---|
| 1200 × 600 × 10 mm | 3 mm | 2.5 m | 0.12 kg |
| 600 × 600 × 10 mm | 3 mm | 3.3 m | 0.16 kg |
| 600 × 300 × 9 mm | 3 mm | 5.0 m | 0.22 kg |
| 450 × 450 × 9 mm | 3 mm | 4.4 m | 0.19 kg |
| 300 × 300 × 8 mm | 3 mm | 6.7 m | 0.26 kg |
| 400 × 250 × 8 mm | 2 mm | 6.5 m | 0.17 kg |
| 300 × 100 × 7 mm metro | 2 mm | 13.3 m | 0.30 kg |
| 200 × 100 × 7 mm metro | 2 mm | 15.0 m | 0.34 kg |
| 100 × 100 × 6 mm | 2 mm | 20.0 m | 0.38 kg |
| 25 × 25 × 4 mm mosaic | 2 mm | 80.0 m | 1.02 kg |
Cement-based grout at 1.6 kg per litre, before wastage. Calculated with the tool on this page. Brands such as Mapei, BAL and Ultra Tile list similar figures.
Grout calculator examples for real UK projects
We ran each project through the calculator with 10% wastage. The differences between them genuinely surprised us.
Case study 1: small bathroom floor
A 2.4 × 1.8 m floor with 600 × 300 × 9 mm porcelain and 3 mm joints
Case study 2: bathroom walls, metro or larger tiles?
13.42 m² of wall after deducting the door, window and bath, with 2 mm joints
That 98% figure is a trap. Some grout inevitably remains on the float, in the bucket and in the sponge. We would never rely on one 2.5 kg bag here.
Case study 3: mosaic shower floor with epoxy grout
A 900 × 900 mm shower tray area with 25 × 25 × 4 mm mosaics and 2 mm joints
Case study 4: outdoor porcelain patio
20 m² of 600 × 600 × 20 mm outdoor porcelain with 5 mm joints
Outdoors, most people use a cement slurry or a resin jointing compound rather than bathroom grout. Check the coverage on the tub. A firm foundation matters more than the joints. Our guide explains how much MOT Type 1 you need underneath.
What joint width should I use?
Joint width affects both the appearance and the quantity. Doubling the joint width doubles the grout requirement. These widths suit most UK projects.
| Tile or situation | Typical joint | Why |
|---|---|---|
| Rectified porcelain | 2 mm | Precise edges allow tight joints |
| Ceramic wall tiles | 2 mm | Clean lines on small tiles |
| Standard floor tiles | 3 mm | Absorbs small size variations |
| Natural stone and handmade tiles | 3–5 mm | Irregular edges need wider joints |
| Outdoor porcelain paving | 3–5 mm | Allows drainage and movement |
| Underfloor heating | 3 mm, flexible grout | The floor moves as it warms |
BS 5385 guidance generally suggests at least 2 mm on walls and 3 mm on floors. Never butt-joint tiles without any gap. Tiles expand slightly with temperature, and tight joints can crack or lift. The BS 5385 code of practice covers joint and movement joint rules in detail.
Cement grout or epoxy grout?
Most UK properties use cement-based grout. Epoxy costs more and requires more skill, yet it resists stains and water almost completely. BS EN 13888 classifies both types.
| Detail | Cement-based grout (CG2) | Epoxy grout (RG) |
|---|---|---|
| Typical density | about 1.6 kg/L | about 1.5–1.6 kg/L |
| Price | £13.50–£28 for 5 kg | considerably higher per kg |
| Stain resistance | Good once sealed | Excellent, no sealer needed |
| Working time | Relaxed | Short, so mix small amounts |
| Best for | Walls, floors, most bathrooms | Showers, kitchens, wet rooms, mosaics |
Here is our honest opinion. Epoxy justifies its price on shower floors and kitchen worktops, where mould and stains develop quickly. On a dry hallway floor, a quality cement grout performs equally well for a fraction of the cost.
The Tile Association publishes technical guidance on grout selection.
Grout cost per m² in 2026
We checked UK retailer listings in October 2026. Grout is usually the least expensive material on any tiling project.
| Project | Grout per m² | Approx. cost per m² |
|---|---|---|
| 600 × 600 mm floor, 3 mm joint | 0.16 kg | about 50p–£1 |
| Metro wall, 2 mm joint | 0.30 kg | about 90p–£1.85 |
| Mosaic, cement grout | 1.02 kg | about £3–£6.30 |
| Mosaic, epoxy grout | 0.99 kg | several times higher |
Based on £13.50–£28 per 5 kg cement grout bag, including 10% wastage. Prices checked October 2026.
Because grout costs so little, never stretch the final bag. One additional bag costs a few pounds, while repairing a patchy wall costs an entire weekend. Enter your own bag price above for an exact figure.
Common grouting mistakes we see
Our perspective changed while researching this page. We originally expected quantity to cause most problems. In reality, poor technique causes equally many.
- Grouting too early. Wait until the adhesive sets, usually 24 hours for standard products.
- Adding extra water. Overly wet mixes shrink, crack and dry to an inconsistent, lighter shade.
- Mixing the whole bag. Prepare only the quantity you can apply within the working time.
- Leaving the haze too long. Wipe with a damp sponge once the grout firms, then buff off the haze.
- Grouting internal corners. Use flexible silicone where walls meet floors, baths and trays.
- Skipping the sealer. Cement grout absorbs stains unless you apply sealer after curing.
Raking out old grout and cutting tiles creates fine silica dust. HSE explains the risks in its construction dust guidance. If the tiles themselves sound hollow, read our guide to checking hollow tiles before repair before regrouting. Planning a new floor? Count the tiles first with our tile calculator.
Grout calculator FAQs
How our grout calculator works out the figures
The calculator converts your area to square metres. It calculates the joint volume per m² using your tile dimensions, thickness and joint width. Then it multiplies by grout density, adds wastage and rounds up to whole bags.
This is the identical joint-volume methodology that grout manufacturers use in their coverage tables. Every case study on this page came straight from the calculator. Prices reflect UK listings checked in October 2026.
Remember that shower wall with two bare rows and a mismatched second bag? Buying the full amount from one batch would have prevented it. Last reviewed: October 2026. Treat results as estimates and check your grout data sheet.
Which tiles are you grouting, and what joint width have you chosen? Tell us through our contact page. We read every message, and good questions often shape future guides.