Thinset Calculator — Bags of Mortar for Tile
Enter your tile area and trowel-notch size to get how many 50 lb bags of thinset mortar you need.
As an Amazon Associate this site may earn from qualifying purchases.
How it works
bags = ceil(area ÷ coverage per bag); coverage depends on the trowel-notch size
Thinset by trowel size (50 lb bag, per 100 sq ft)
| Trowel notch | Coverage per bag | Bags per 100 sq ft |
|---|---|---|
| ¼ in (mosaic / small tile) | ~95 sq ft | 2 |
| ¼ × ⅜ in (8–12 in tile) | ~60 sq ft | 2 |
| ½ in (12–16 in tile) | ~40 sq ft | 3 |
| ¾ in (large-format tile) | ~30 sq ft | 4 |
Coverage is for a 50 lb bag and drops as the trowel notch (and tile size) grows. Back-buttering large tile uses more. Always round up and keep a spare bag.
Frequently asked questions
How much thinset do I need per square foot?
It depends on the trowel size. A 50 lb bag covers roughly 95 sq ft with a ¼-inch trowel (small tile), about 60 sq ft with a ¼×⅜-inch trowel (12-inch tile), and 30–40 sq ft with a ½–¾-inch trowel for large-format tile.
What size trowel should I use for tile?
Match the notch to the tile: ¼-inch for mosaics and small tile, ¼×⅜-inch for 8–12-inch tile, and ½-inch or larger for 16-inch and bigger. Larger tile needs more mortar to bed fully and avoid voids.
What is the difference between modified and unmodified thinset?
Modified thinset has polymers for a stronger, more flexible bond — typical for tile over concrete or cement board. Unmodified is required under many large porcelain tiles and over uncoupling membranes. Follow the tile and membrane manufacturers’ specs.