Tile & Grout Calculator

Tiling Guide

What should I know about Waste Allowance by Pattern?

Straight grid pattern: 10% waste allowance. Offset / brick bond (each row shifted by half a tile): 10–12% waste — the offset cuts increase edge waste slightly. Diagonal / 45° pattern: 15–20% waste — cutting tiles to fit a diagonal layout produces significantly more offcuts. Herringbone: 15–20% waste. For complex shapes or rooms with multiple features (bays, alcoves, columns): add an additional 5%. Always buy tiles from the same batch (same batch number on box) — colours and sizes can vary noticeably between production runs, even for the same product line.

What should I know about Grout and Adhesive Calculations?

Grout quantity depends on tile size, gap width, and tile depth. A rough guide: for 300×300mm tiles with 3mm gaps, approximately 0.5–0.8kg grout per m². For larger tiles (600×600mm): approximately 0.3–0.5kg per m². Tile adhesive: standard coverage is 3–4kg per m² for standard adhesive (notched trowel application). For large-format tiles (over 600mm), use flexible adhesive and back-butter the tile as well. Always apply adhesive in one direction with a notched trowel — this ensures consistent coverage and the correct adhesive bed depth across the whole area.

What's the key thing to understand about Surface Preparation?

Tiling over paint: remove all loose paint, sand to rough up, prime with a tile primer (PVA + water will not bond adequately). Tiling over plasterboard: use waterproof tile backer boards in wet areas (shower, bath), not standard plasterboard — moisture causes the plasterboard to swell and the tiles to lift. Over existing tiles: possible if tiles are fully adhered, level, and sound — check by tapping (hollow sound = loose). Use a tile primer and flexible adhesive. Over floors: the subfloor must be solid, level, and free of movement, since tiles laid over a flexing or uneven surface are prone to cracking or coming loose.

What's the key thing to understand about Setting Out and Starting Point?

Never start tiling from a corner — corners are never truly square, causing tiles to splay out visibly. Find the centre of the wall or floor using chalk lines, set out from the centre, and adjust so that cut tiles at the edges are equal width (and ideally over half a tile wide). For floors, 'dry lay' tiles across the room first to check your layout visually before committing adhesive. Use tile spacers consistently — even 1mm variation in gaps is visible. Diagonal patterns start from the exact room centre point, working outward symmetrically in both directions to avoid an unbalanced, lopsided layout.

What should I know about Grout Joint Width and Consumption?

Grout consumption scales with joint width, tile size, and tile thickness — wider joints or thicker tiles both mean more grout volume per metre of joint. The standard estimate uses: grout needed (kg) ≈ (joint width mm × joint depth mm × joint length m × 1.6) / 1000, where 1.6 is an approximate density factor for cement-based grout; a simpler rule of thumb many tilers use is that doubling joint width roughly doubles grout consumption for the same tile size. Larger format tiles need noticeably less grout per square metre than small mosaic tiles for a given joint width, because fewer, longer joints cover the same area compared to many short joints between small tiles — this is why mosaic tile sheets often specify disproportionately high grout coverage requirements relative to their tile area.

What do I need to know about Epoxy vs Cement-Based Grout?

Cement-based grout (the standard, cheaper option) is porous and can stain or absorb water over time unless sealed, making it less suitable for heavily used wet areas or dark grout lines next to light tiles where staining would show clearly. Epoxy grout is non-porous, highly stain- and chemical-resistant, and doesn't need sealing, making it the better choice for kitchen worktops, commercial kitchens, and swimming pool surrounds — but it costs considerably more (often 3-5x cement grout), has a shorter working time before it starts to cure (meaning less area can be grouted per batch), and is noticeably harder to clean off tile faces if not wiped promptly. For most domestic bathroom and kitchen floor/wall tiling, a good quality cement-based grout with a sealant applied after curing offers a reasonable balance of cost and performance without epoxy's working-time challenges.

What should I know about Grout Haze Removal and Curing Time?

Grout haze — the dull, cloudy film left on tile surfaces after grouting — forms when grout residue dries on the tile face rather than being fully wiped off while still workable, and it's much easier to prevent than to remove later. Wipe tiles diagonally across the joints with a damp (not wet) sponge as soon as the grout has firmed up enough not to be pulled out of the joints, usually 15-30 minutes after application, then follow with a drier cloth buff once a light haze reappears as the surface dries, typically after another 20-40 minutes. If haze is allowed to fully cure (which can take 24-72 hours depending on the grout and conditions), it often needs a dedicated grout haze remover or diluted acidic cleaner to shift, and these can etch natural stone or certain glazes, so always test on an offcut first. Full grout cure — the point at which it reaches its final strength and can be sealed or exposed to regular water — typically takes 7 days for cement-based grout, even though it may feel dry to the touch within hours, so avoid heavy traffic, sealing, or soaking the area (e.g. a new shower floor) until that curing period has passed.

Worked Example: Grout and Adhesive for a Bathroom Floor

A bathroom floor measuring 2.5m × 2m, tiled with 300mm × 300mm tiles and 3mm grout joints.

This small bathroom floor needs around 62 tiles allowing for cutting waste, roughly 1.75kg of grout given the relatively tight 3mm joints and large tile size (fewer, wider tiles mean proportionally less joint length and therefore less grout than the same area tiled with small mosaic-format tiles), and around 18kg of tile adhesive. Floor tiling generally uses noticeably more adhesive per square metre than wall tiling because floor tiles are typically larger, heavier, and laid with a deeper adhesive bed to accommodate the slight unevenness of a screed or sub-floor, whereas wall tiles are thinner and lighter and need only a thin, even adhesive layer to hold securely.

Choosing Grout Colour and Sealing

Grout colour has a bigger visual impact on a finished tiling job than many people expect, because grout lines, even at just a few millimetres wide, create a grid pattern across the entire tiled area that either disappears visually (grout matched closely to tile colour) or becomes a deliberate design feature (a contrasting grout colour that emphasises each individual tile's shape and the overall laying pattern). Light-coloured grout looks clean when new but shows dirt, grease, and mould considerably faster than darker grout, particularly in kitchens and bathrooms where grease splashes or persistent damp are common — many tilers now default to a mid-grey or darker grout specifically to reduce the visible staining that white or pale grout develops within just a year or two of use. Cement-based grout, unlike epoxy, is porous and should be sealed with a grout sealer once fully cured (typically after the manufacturer's recommended curing period, often around 2-4 weeks) to reduce staining and water absorption, especially in wet areas like shower floors and splashbacks — this sealing step is frequently skipped by DIY tilers but makes a measurable difference to how grout looks and performs over the following years. Resealing is generally recommended every 1-2 years in high-moisture areas as the sealer wears away from regular cleaning and water contact, and a quick way to check if resealing is due is to drip a small amount of water onto the grout line: if it soaks in and darkens the grout within a minute rather than sitting as a bead on the surface, the seal has worn through and needs renewing.