DITRA Calculator
Your floor
DITRA to buy
1 × 150 sq ft
- Floor area
- 100 sq ft
- Membrane with waste
- 110 sq ft
- Bond coat (50 lb bags)
- 1
- Tile coat (50 lb bags)
- 2–3
- Bond trowel
- 11/64" × 11/64" square (DITRA trowel)
- Tile trowel
- 1/4" × 3/8" square or U-notch (or larger)
Rolls are the combination with the least left over.
Tools the pros use for this job
Schluter-DITRA Membrane
The membrane itself, in 54, 150 and 323 sq ft rolls.
DITRA Trowel 11/64 in
DITRA Trowel 11/64 in
The notch Schluter designed for bonding DITRA to the floor.
Check price on AmazonThe notch Schluter designed for bonding DITRA to the floor.
Unmodified Thin-Set
Unmodified Thin-Set
Schluter's instructions call for unmodified or Schluter-SET mortars.
Check price on AmazonSchluter's instructions call for unmodified or Schluter-SET mortars.
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Prices as of Oct 1, 2026, 4:37 AM UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
DITRA rolls and mortar by floor size
| Floor (+10%) | Rolls | Bond bags | Tile bags |
|---|---|---|---|
| 40 sq ft | 1×54 | 1 | 1–1 |
| 60 sq ft | 2×54 | 1 | 2–2 |
| 100 sq ft | 1×150 | 1 | 2–3 |
| 150 sq ft | 1×150 + 1×54 | 1 | 3–4 |
| 200 sq ft | 1×150 + 2×54 | 2 | 4–5 |
| 300 sq ft | 2×150 + 1×54 | 2 | 6–8 |
Mortar rates from Schluter-Systems' DITRA & DITRA-XL installation notes; roll sizes as sold (DITRA54, DITRA150, DITRA323). Always read the mortar bag and the current DITRA handbook for your substrate.
Do this math on the job site — in the free app
Smart Tile Calculator for Android: offline, in your pocket, free.
How this calculator works
Membrane. Floor area plus the waste you allow for cuts, rounded up to the roll sizes DITRA is sold in (54, 150 and 323 sq ft, 39 in wide). Sheets are butted, not overlapped, so waste is only offcuts.
Bond coat. Schluter: bonding DITRA to the substrate with the DITRA trowel (11/64 × 11/64 in square-notch) uses one 50 lb bag per 150 sq ft (DITRA-XL with its trowel: 100 sq ft). A 1/4 × 3/16 in or 5/16 × 5/16 in V-notch can also be used.
Tile coat. Setting tile on DITRA with a 1/4 × 3/8 in square- or U-notch uses one bag per 40–50 sq ft (DITRA-XL: 35–45), because the mortar also fills the membrane's cavities.
Worked example. A 10 × 10 ft floor, 10% waste: 110 sq ft of membrane — one 150 sq ft roll. Bond coat 100 ÷ 150 = 1 bag; tile coat 100 ÷ 50 to 100 ÷ 40 = 2 to 3 bags.
Frequently asked questions
What size trowel for DITRA?
To bond DITRA to the floor, Schluter's DITRA trowel (11/64 × 11/64 in square-notch), or a 1/4 × 3/16 in or 5/16 × 5/16 in V-notch. To set tile on top, a 1/4 × 3/8 in square- or U-notch, or larger for big tile so the cavities fill and the tile is fully supported.
How much thin-set do I need for DITRA?
Two amounts. Under the membrane, about one 50 lb bag per 150 sq ft with the DITRA trowel. On top, setting tile with a 1/4 × 3/8 in notch, one bag per 40–50 sq ft. A 100 sq ft floor needs 1 bag plus 2–3 bags.
What sizes does DITRA come in?
Rolls of 54, 150 and 323 sq ft, all 39 in (3 ft 3 in) wide. DITRA itself is about 1/8 in (3.5 mm) thick; DITRA-XL is the 5/16 in version for transitions to thicker floor coverings.
Do DITRA seams overlap?
No. Schluter's instructions have adjacent sheets simply butted at the ends and sides. Only waterproof installations add KERDI-BAND over the seams, set in mortar.
Is DITRA worth it over cement board?
DITRA adds uncoupling — it lets the tile and subfloor move independently — and is only 1/8 in thick, which keeps transitions low. Cement board adds stiffness but no uncoupling. Either way the floor itself must be stiff enough: check it with the floor deflection calculator.
Related calculators
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- Floor Tile CalculatorTiles and boxes for any floor, by room dimensions and tile size.
- Floor Deflection CalculatorJoist deflection and pass/fail at L/360 for porcelain or L/720 for natural stone.
- Tile Trowel Size CalculatorWhich notch for your tile size, mortar coverage to check for, and bags of thinset.
- Backer Board CalculatorCement board sheets, screws, and tape for floors and walls.
Guides worth reading next
- How to Measure a Room for Tile (Step by Step)Measure any room for floor or wall tile: handle closets and alcoves, convert inches to decimals, subtract fixtures, and add the right waste percentage.
- Choosing the Right Tile Size for Your RoomHow tile size changes a room: when 12×24 beats 4×4, why small rooms can take large tile, grout line math, and the flatness rule for big formats.
- Sanded vs Unsanded vs Epoxy Grout: Which One Do You Need?Grout types explained by joint width and location: when sand scratches tile, why epoxy wins in showers, and how much of each type a bag actually covers.