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Thinset & Tile Adhesive Calculator

Work out the adhesive a tiling job needs from the trowel notch, which is what actually sets the coverage.

  • Answers as you type
  • Every formula cited
  • Calculated in your browser
SettingsSettings for this calculationUS
Market
Imperial · sales tax
Net tiling area.

Net — openings, fixtures and anything not being tiled taken out. Then treat the answer with care, because area is not the largest term in thinset coverage: the trowel notch and the tile's own back profile move the quantity more than a modest area error does, and a large-format tile that has to be back-buttered to reach full bedding can use close to twice what the same area of small tile uses.

Notch size governs how much adhesive stays on the wall.

The notch, not the tile, sets the consumption. Using a small notch under a large tile is the most common cause of hollow spots and later cracking, because the ridges cannot collapse enough to fill the bed.

A skim coat on the tile back as well as the substrate.

Required in practice on large-format tile and on anything in a wet area, where TCNA calls for 95% coverage. It is the reliable way to get there, and it adds roughly a third to the adhesive used.

Weight of the bags you are buying.

Enter the bag you can actually order, so the answer comes out in bags rather than in a quantity nobody sells. Sizes differ by brand and by region, so check rather than assume. Order in whole bags with a little over, too: a part-used bag of thinset does not survive long in a damp store, and running short mid-floor means a joint where the work stopped.

Adhesive required

3 bags

Medium confidence

Coverage rates are typical for cement-based adhesive. Check the specific product — rates vary by 20% between brands and between standard and lightweight formulations.

Adhesive required
133.13 lb
Coverage rate
1.02 lb/sq ft
Bag size
50 lb
Surplus in the last bag
16.87 lb
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • Coverage by notch size — CUSTOM Building Products VersaBond: data sheet TDS-119 (published 12/12/2023) gives 85-95 sq ft (7.9-8.8 m²) per 50 lb (22.68 kg) bag on a 1/4 in square notch, 2.6-2.9 kg/m²; the product page's coverage table gives 42-47 sq ft (3.9-4.4 m²) on a 1/2 in square notch, 5.2-5.8 kg/m²
  • ARDEX S27, S28 and X7 data sheets: about 1.0, 1.1 and 1.3 kg of powder per m² per mm of adhesive bed, with S27 covering about 6.4 m² per 20 kg bag at the 3 mm bed a 6 mm square notch leaves. The table here is about 0.5 kg/m² per mm of notch: on ARDEX's line and a little above VersaBond's table, so it errs toward a spare bag. Larger tiles take larger notches and consume substantially more
  • TCNA requires 80% mortar coverage for dry interior and 95% for wet areas and exterior — back-buttering is usually needed to achieve it on large formats and in wet areas

Inputs used

Area to tile
130 sq ft
Trowel notch
3/8 in square — up to 24 in tile (~1.02 lb/sq ft)
Back-buttering
No
Bag size
50 lb

Intermediate steps

Adhesive required
133.13 lb
Coverage rate
1.02 lb/sq ft
Bag size
50 lb
Surplus in the last bag
16.87 lb
Final result3 bags

Confidence note: Coverage rates are typical for cement-based adhesive. Check the specific product — rates vary by 20% between brands and between standard and lightweight formulations.

What this calculation does not cover

  • An uneven substrate consumes considerably more than these figures. Levelling first is cheaper than filling with adhesive, and it performs better.
  • Does not cover a levelling compound, a decoupling membrane or a waterproofing layer, all of which are separate materials.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

11.4 ft3.48 m11.4 ft3.48 mequivalent area130 sq ft12.08 m²5 ft1 m

Part of bigger jobs

This trade is one line of several job takeoffs. Run the whole job and every other trade comes back with it, off the same measurements.

Or plan the space itself: measure it once, doors and windows included, and this figure comes back worked out on that space, with what goes with it.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-05 · in the site-wide review of 2026-09-06 · v1.0.1

Regulatory standards & verification citations3
  1. Coverage by notch size — CUSTOM Building Products VersaBond: data sheet TDS-119 (published 12/12/2023) gives 85-95 sq ft (7.9-8.8 m²) per 50 lb (22.68 kg) bag on a 1/4 in square notch, 2.6-2.9 kg/m²; the product page's coverage table gives 42-47 sq ft (3.9-4.4 m²) on a 1/2 in square notch, 5.2-5.8 kg/m²
  2. ARDEX S27, S28 and X7 data sheets: about 1.0, 1.1 and 1.3 kg of powder per m² per mm of adhesive bed, with S27 covering about 6.4 m² per 20 kg bag at the 3 mm bed a 6 mm square notch leaves. The table here is about 0.5 kg/m² per mm of notch: on ARDEX's line and a little above VersaBond's table, so it errs toward a spare bag. Larger tiles take larger notches and consume substantially more
  3. TCNA requires 80% mortar coverage for dry interior and 95% for wet areas and exterior — back-buttering is usually needed to achieve it on large formats and in wet areas
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Tools and safety for this job

To mix adhesive or mortar. Generic types, no brands, no prices.

Protection this work requires

  • Cutting or grinding concrete, masonry, screed, tile or fibre-cement board releases respirable silica: cut wet or extract at the tool, and wear a P2/N95 respirator at minimum — a nuisance dust mask does not filter it.
  • Wet cement and lime burn skin and eyes painlessly until the damage is done: waterproof gloves to EN 374, safety glasses whenever the mix can splash, and never kneel in wet mix in permeable trousers.
Show the 3 tools this job needs

Essential

  • Mixing bucket or tub

  • Paddle mixer

Optional

  • Shovel and spade

what each tiling tool is for, and the spec that decides which to buy where one does.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

  • Falls, Tanking and the Gully in a Wet Room Flooruses this calculator

    A walk-in shower cut into a floor that already exists: the depth budget under it, the gradient band the codes barely leave open, and the tanking above it.

  • Setting Floor Tileuses this calculator

    Floor tile is set out before it is set: the first two lines you strike decide every cut, joint and threshold in the room.

  • Setting Out Wall Tiles in a Bathroomuses this calculator

    A bathroom wall offers more datums than a grid of courses can honour — rim, ceiling, niche, window — and setting out is choosing which one gets the full course.

Called something else where you work? Lime binders · Tile adhesive — the term in each market, how close the equivalence really is, and the standard that governs it.

Already have some? How much floor tile will my bags of thinset set?

Worked example: Bathroom gutted and retiled — step 6 of 9

Already gone wrong? My tiles are coming loose or sounding hollow · My grout is cracking, powdering or falling out

How to calculate thinset & tile adhesive in 5 steps

  1. Area to tileNet tiling area.
  2. Trowel notchNotch size governs how much adhesive stays on the wall.
  3. Back-butteringA skim coat on the tile back as well as the substrate.
  4. Bag sizeWeight of the bags you are buying.
  5. Adhesive requiredThe tool computes the adhesive required from those figures and shows the formula, its sources, and a confidence rating alongside it.

Adhesive required by area to tile

Page defaults, not your figures above.

Area to tileAdhesive required (bags)
100 sq ft3
150 sq ft4
200 sq ft5
250 sq ft6

Frequently asked questions

Why does the trowel notch decide the quantity?
Because it sets the depth of the adhesive ridges, and it is those ridges that collapse to form the bed. A 6 mm notch lays about 3 kg/m²; a 20 mm half-round about 9. The tile size matters only because it determines which notch you must use.
What is back-buttering and do I need it?
A skim of adhesive on the back of the tile as well as the substrate. On large-format tile, and on tile in a wet area where the bar is higher, it is the practical way to reach the coverage the standards require — 80% for dry interior, 95% for wet areas — because a notched bed alone rarely achieves it. It adds about a third to consumption.
Why do I keep running out?
Almost always substrate flatness. Adhesive fills every hollow, and a floor that is 5 mm out over two metres absorbs a surprising amount of it. Levelling first costs less than the extra adhesive and gives a better result — filling deviation with adhesive is how tiles end up hollow-sounding.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.