Grout calculator
Ten square metres of 300 × 300 mm tiles with 3 mm joints filled 8 mm deep take about 1.6 litres of grout, a little over 2 kg. Enter your tiles and joints before you buy bags. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Area
- 10
- Tile length
- 300
- Tile width
- 300
- Joint width
- 3
- Joint depth
- 8
- Area m2
- 10
- Tile length mm
- 300
- Tile width mm
- 300
- Joint width mm
- 3
This grout calculator estimates how much grout a tiled floor or wall actually needs once you know the tiled area, the tile length and width, the joint width between tiles, and the joint depth. It uses a geometric joint-fraction model: each tile sits in a module that includes its share of the joints, the fraction of the surface that is joint is one minus the tile face over that module, and volume equals area times that fraction times joint depth. Weight follows by multiplying volume in litres by bulk density, defaulting to a typical cementitious value of 1.6 kilograms per litre. Joint depth is an independent input, so you can fill only part of the tile thickness when a specification calls for a shallower bed. The engine is pure arithmetic with no network calls, no sampling, and no date-dependent shortcuts.
Where a grout take-off fits in DIY, trade quotes, and software
Homeowners meet this calculation when a bathroom remodel needs a second bag of sanded grout after a surprise wide joint, or when a kitchen splashback order must not overshoot the budget. Estimators embed the contract in take-off tools so a room schedule of tile size, joint width, joint depth, and square metres becomes litres and kilograms without a spreadsheet full of hidden cells.
Product and education tools show learners why 600 by 600 tiles with two millimetre joints use far less grout per square metre than 100 by 100 mosaics with the same joint width, and why doubling joint depth doubles volume at a fixed fraction. Pair it with tile-count or area helpers when you are building a small lab of free, deterministic site calculators, and keep a margin for waste, hollows, and cleaning losses that your site conditions require beyond the pure geometric fill.
This is a grout volume and weight take-off, not a mortar-bag count from brick quantity and not a concrete-block core fill: those are different search intents with different inputs.
What you can do with it
DIY bathroom and floor shopping lists
Convert measured square metres, tile size, joint width, and joint depth into litres and kilograms of grout before you buy bags at the merchant.
Trade quotes and take-offs
Turn room schedules of tile dimensions, joint size, and area into reproducible volume and weight estimates for written quotes.
FAQ
What does the grout calculator cost?
It is free in your browser on this page.
What happens if joint width or a dimension is negative?
Joint width, tile length, tile width, joint depth, and area must all be strictly positive finite numbers; a negative value does not define a groutable surface.
Which units should I send?
Tile length, tile width, joint width, and joint depth are millimetres. Area is square metres. Density, when you override the 1.6 kg/L default, is kilograms per litre. Convert other unit systems before calling.
Does the result include waste or bag sizes?
No. The core volume and weight are geometric fill only.
How much grout do I need for 10 m² of 300 x 300 mm tiles?
About 1.6 litres, a little over 2 kg, with 3 mm joints filled 8 mm deep and a typical density of 1.6 kg per litre. Add your own margin for cuts, hollows and cleaning.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/build/grout \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"area":10,"tile_length":300,"tile_width":300,"joint_width":3,"joint_depth":8}'const res = await fetch("https://api.kit.forhosting.com/build/grout", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"area": 10,
"tile_length": 300,
"tile_width": 300,
"joint_width": 3,
"joint_depth": 8
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/build/grout",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"area": 10,
"tile_length": 300,
"tile_width": 300,
"joint_width": 3,
"joint_depth": 8
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/build/grout", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"area":10,"tile_length":300,"tile_width":300,"joint_width":3,"joint_depth":8}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"area":10,"tile_length":300,"tile_width":300,"joint_width":3,"joint_depth":8}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/build/grout", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"area": 10,
"tile_length": 300,
"tile_width": 300,
"joint_width": 3,
"joint_depth": 8
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "build.grout",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs | 1000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Negative joint width or any negative dimension is rejected as invalid_input instead of a hollow zero. Use it free in the browser for DIY shopping lists and contractor take-offs, or call the API at $0.002 per successful request when estimating software needs a reproducible volume and weight.
What grout volume means and what the response contains
Grout fills the open network of joints between tiles, so the volume you mix and the mass you buy depend on how wide those joints are, how deep the grout bed is, how large each tile face is, and how many square metres you cover. Larger tiles leave fewer linear metres of joint per square metre; wider joints and deeper beds increase volume quickly. There is no catalogue of brand bag sizes and no moisture or waste fudge baked into the core number: you get the geometric fill so you can add your own waste percentage for cuts, hollows, and leftovers. Joint depth is not assumed equal to tile thickness: wall tiles are often grouted shallower than the biscuit, mosaic sheets may need a full-depth fill, and a specifier can call for a partial bed to leave room for movement. This calculator returns the parsed tiled area in square metres, tile length and width in millimetres, joint width and joint depth in millimetres, the density used, the joint fraction as a pure number between zero and one, grout volume in both cubic metres and litres, the weight in kilograms, and a short formula string you can audit. Rejected cases include missing area, tile length, tile width, joint width, or joint depth, non-finite values, magnitudes above the documented ceiling, and any of those dimensions that is zero or negative, because a negative joint or a negative area does not define a groutable surface.
How dimensions, joints, and density are read and stay reproducible
Computation builds the module area as length plus joint times width plus joint, subtracts the tile face fraction from one, multiplies by area and by joint depth converted from millimetres to metres, converts cubic metres to litres, then multiplies by density. Rounding uses a stable twelve-significant-figure conversion and collapses negative zero for clean comparisons. Send tile_length and tile_width in millimetres for every tile, square or rectangular, with aliases length, width, tile_l, tile_w, L, and W so forms and query strings can reuse the same contract. Joint width accepts joint_width plus aliases joint, gap, grout_width, and j; joint depth accepts joint_depth plus depth, thickness, grout_depth, and tile_thickness when the bed really does match the biscuit. Area accepts area, total_area, surface, sqm, and m2 and is always square metres. Optional density defaults to 1.6 kilograms per litre for cement-based grout and may be set via density, rho, bulk_density, or kg_per_l when the manufacturer publishes a different bulk density for epoxy or fine sanded products. A negative joint_width, a negative tile_length, a negative tile_width, a negative joint_depth, or a negative area fails with invalid_input naming the field and stating that the value must not be negative. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing the fraction formula yourself.
Where a grout take-off fits in DIY, trade quotes, and software
Tile fitters and small contractors use the same numbers to turn a measured floor plan into a shopping list before they leave the yard, setting joint_depth independently when wall tiles are grouted shallower than floor tiles on the same job. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — lets you move from a phone check on site to an automated pipeline without changing the mathematical result.
Integration use cases
Estimating software and CI fixtures
Seed deterministic volume_l and weight_kg values for unit tests, property checks, and automated pipelines without re-deriving joint geometry.
Technical questions
How is grout volume and weight calculated?
joint_fraction = 1 − (L×W)/((L+j)×(W+j)); volume in cubic metres = area_m² × joint_fraction × (joint_depth_mm/1000); volume in litres = volume_m³ × 1000; weight_kg = volume_L × density (default 1.6 kg/L).